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C.OFflUGHT DEPOSHi 



PRACTICAL TANNING 



PRACTICAL 

TANN ING 



A HANDBOOK OF MODERN PRACTICE 

AND PROCESSES AS APPLIED IN THE 

MANUFACTURE OF LEATHER 

AND ALLIED PRODUCTS 

BY 

ALLEN ROGERS, Ph.D. 

In charge of Industrial Chemistry and Leather Courses 
at Pratt Institute, Brooklyn, N. T. 

Partly Based on the Third Edition of "Practical Tanning," 
by Louis A. Flemming 

ILLUSTRATED BY ONE HUNDRED AND TWENTY- FOUR 
ENGRAVINGS 



NEW YORK 
HENRY CAREY BAIRD & CO., Inc. 

Publishers of Mechanical and Industrial Books 

2 West 45TH Street 
1922 






Copyright, 1Q22, by 
HENRY CAREY BAIRD & CO., Inc. 



PRINTED IN U. S. A. 




APR 29 1922 
'CU601479 



P R E F ACE 

In presenting this book on leather manufacture I have en- 
deavored to Arrange the text with as little repetition as pos- 
sible. The various processes have- been taken up in the order 
of their sequence, and where the same procedure is carried 
out for various classes I have attempted to point out the most 
satisfactory method for each classification. For example, the 
processes of depilation are included in one chapter, and 
the various ways of accomplishing this end are thoroughly 
discussed. 

Being intended primarily for those interested in the actual 
production of leather, this book deals with the subject from 
the practical rather than from the theoretical standpoint, and 
it is hoped that by following the instructions given the tanner 
may find suggestions which will serve to improve his product 
or assist him in producing new varieties of leather. Where it 
has been found necessary to discuss the underlying scientific 
principles, these are stated in as simple a manner as possible. 
A chapter on analytical methods has been included, not only 
for the benefit of the works chemist and student, but also 
in order that the practical man in the plant may be able to 
obtain some idea of the methods necessary for the chemical 
control of the material he handles. 

In addition to the common standard methods of tanning, 
a number of unusual processes are given, as well as descrip- 
tions of some of the more recent products which have been 
introduced as a substitute for the ordinary materials employed 
in leather manufacture. 

Much of the matter herein has been taken from the previous 
volumes of "Practical Tanning," by Louis A. Flemming, and, 
in addition, many processes have been included as a result 
of my personal experience. In many instances also, material 



viii PREFACE 

has been drawn from trade papers and technical journals, as 
well as from notes furnished by men who are well known in 
the industry. In presenting this material it is desired to give 
full credit to these sources of information, which will be found 
in the text. 

In a book of this character, covering so wide a range of 
methods, there are always points where a difference of opin- 
ion may exist, and it is hoped, therefore, that wherever this 
occurs, the reader will feel at liberty to communicate with me, 
as any constructive criticism will always be greatly appreciated. 

Allen Rogers 
Pratt Institute, 
Brooklyn, N. Y. 

April 10, 1922. 



CONTENTS 

Chapter I 

HIDES AND SKINS ! - 55 

Classification of pelts. Dry or flint hides. Dry-salted hides. 
Green-salted hides. Salt stains. Packer hides. Stuck-throats. 
Cut-throats. Flaying. Curing. Taking-up hides. Sweep tare. 
Grubs. Grub allowance. Hide selections— Native steers: Spready 
hides: Texas steers: Colorado steers: Cowhides: Bull hides: Coun- 
try hides. Kips. South American hides. Anglo-American hides. 
Swiss and Bavarian hides. Calfskins. Horsehides. Goatskins- 
Curing: Spanish goatskins: German goatskins: Italian goatskins: 
Southern Europe goatskins: Turkish goatskins: Russian goatskins: 
North African goatskins: South African goatskins: Arabian goat- 
skins: Indian goatskins: Chinese goatskins. South American goat- 
skins. Hogskins. Sheepskins— Sheep kids: Sheep ticks: Lice: Fly- 
blow. Other hides and skins. Disinfection of hides. Regulations 
of the U. S. Government. Hide structure. Conservation of skin 
substance — Zinc chloride: Formaldehyde. 

Chapter II 

SOAKING S6_7 ° 

Fresh or market hides. Green-salted hides. Dry-salted hides. 
Dry hides— Stocks: Fleshing: Putrid soaks: Chemical soaks: Pad- 
dle soaking. Kips. Calfskins— Green-salted skins: Dry skins. 
Sheepskins— Fresh skins: Dry skins: Green-salted sheepskins: Dry 
sheepskins. Goatskins— Dried skins: Dry-salted sk:ns: Sodium 
bisulphite. Kangaroo skins— Soaking and softening. Pigskins- 
Washing: De-greasing: Krouse process. Furs and hairskins. 
Formaldehyde raw stock. 

Chapter III 

DEPUTATION 71 " 109 

Sweating— Cold sweat: Warm sweat. Liming— Quicklime: Hy- 
drated lime. Sodium sulphide. Arsenic sulphide. Caustic soda. 
Calcium sulphydrate. Arazym. Unhairing. Methods of depila- 
tion. Liming hides for upper leather— First day: Second day: 
Third day: Fourth day: Fifth day: Sixth day. Sodium sulphide 
process for dry hides. Notes on beam-house work — Arsenic sul- 
phide. Liming for thin grain. Liming for sole leather. Sulphide 
process for sides, kips, or calf — Sodium sulphide and calcium chloride 
on sides and kips. Liming of calfskins. Lime and arsenic. Liming 



x CONTENTS 

of goatskins — Combination process. Depilatory compounds for wool 
skins and hairskins. Depilating glove leather. Patented depila- 
tories — Depilatory paints: Applying the depilatory paint. Liming 
after removal of the wool. Liming for Mocha and castor gloves. 
Method of using arazym on goatskins — Soaking: First day: Third 
day: Fourth day: First liquor: Second liquor: Fifth day. 

Chapter IV 

DE-LIMING, DRENCHING, BATING, PUERING AND 

PICKLING . . ' 110-133 

De-liming — Test for de-liming: Sulphuric acid: Hydrochloric acid: 
Sulphurous acid: Sodium bisulphate: Boracic acid: Carbonic acid: 
Lactic acid: Formic acid: Formic acid and lactic acid drench: 
Butyric acid: Ammonium chloride: Ammonium butyrate: Sodium 
dichromate: Sodium bisulphite: Ammonium phosphate: Zinc sul- 
phate: Coal-tar bates. Drenching — Method of de-liming (drench- 
ing) with bran: Other bran drench ' formulas: Mild fermented 
drench. Puering and bating — Bating with molasses: Bating with 
glucose, sulphur, and yeast: Dog dung: Hen manure: Dermiforma: 
Dr. Rohm's bate "oropon C" for regular packs: Bating process: 
Dr. Rohm's bate "oropon AB" for limed goatskins: Bating, first 
liquor: Temperature: Second liquor: Quantity of oropon for 100 
lb. of skins: Temperature: Martin Dennis' "puerine": First pack: 
Second pack: Third pack: Fourth and all following packs: Puerine 
D. Pickling — Sulphuric acid and salt: Formic acid and salt: Hydro- 
chloric acid and calcium chloride. Pressing grease from pickled 
sheepskins — Gargoyle de-greasing fluid. De-greasing fluid — Recov- 
ered grease. Splitting out of lime. Splitting out of aluminum 
sulphate and salt pickle. Splitting after tanning. Splitting out of 
acid pickle. 

Chapter V 
RAW HIDES: OIL AND ALUM TANNAGE .... 134-157 

Raw hide. Lace leather — Shark-liver oil tannage: Latigo leather: 
Alum-tanned lace leather No. 1: Alum tannage No. 2: Alum tannage 
No. 3: Picker leather: Pyro tan. Chamois leather — Bleaching. 
Rogers' shark-liver oil process. Sheepskin fleshers — Imitation 
castor. White calfskin leather — Tannage: Fat-liquoring: Finishing: 
Formaldehyde tannage: Kid glove leather. White pigskins. Tan- 
ning snake skins with alum and salt. White splits. Splits for 
white shoes. Tanning buckskins. White buckskin. Indian method 
of tanning buckskins. Tanning with formaldehyde. 

Chapter VI 
CHROME TANNAGE 158-213 

Two-bath chrome process. One-bath chrome process. Glazed kid 
manufacture. Two-bath chrome on pickled sheepskins — Sodium 
thiosulphate bath: Neutralizing. Tanolin. One-bath chrome on 



CONTENTS xi 

pickled sheepskins — Process for glove leather. Neutralizing and 
washing chrome sheepskins. White chrome-tanned sheepskins — 
Tanning' in a paddle-vat: Process of alum and chrome tanning. 
New two-bath process of chrome tanning — Neutralizing and wash- 
ing the tanned leather: Neutralizing with borax. Notes and sugges- 
tions. Difference between one-bath and two-bath chrome-tanned 
leathers. Chrome-tanned side leather — One-bath chrome process for 
acid-pickled stock: Prqcess for alumina-pickled grains: Process for 
unsplit sides: Neutralizing and washing. Chrome side glove and 
mitten leather. Chrome-tanned sole leather — Soaking: Liming: 
De-liming: Pickling: Tanning: Other tanning processes. Chrome- 
tanned harness leather — Liming: Bating: Pickling: Tanning: Re- 
tanning. Chrome-tanned belt and strap leathers — Strap leather. 
White side leather — Treatment with flour: Finishing: Tanning with 
aluminum sulphate: Fat-liquoring with acid fat-liquor: Finishing. 
Chrome velvet leather. Chrome-tanned patent leather — Coloring 
and fat-liquoring: Staking and finishing. White chrome. Tanolin 
T — Pickling: First pack: Second pack: Third, fourth, fifth and 
sixth packs: Seventh, eighth, ninth, tenth, eleventh and twelfth 
packs: Tanning: First pack; Second pack: Third, fourth, fifth, sixth 
and seventh packs: Eighth, ninth and tenth packs: Dissolving 
. tanolin T: Neutralizing and washing. To increase suppleness. 
Dissolving chrome-alum. Aluminum bisulphite reduction. Re- 
covery of chrome residues. Chrome-tanned buckskin — White 
chrome buckskin. One-bath chrome tannages. Theory of chrome 
tanning. Calfskin glove and mitten leathers. Chrome lace leather. 
Semi-chrome leather — Splitting and shaving: Stripping the tannage. 
Vegechrome — Pickling: First pack: Second pack: Third, fourth, 
fifth and sixth packs: Seventh, eighth, ninth, tenth, eleventh and 
twelfth packs: Tanning— First pack: Second pack: Third, fourth, 
fifth, sixth and seventh packs: Eighth, ninth and tenth packs: 
Dissolving vegechrome: Neutralizing and washing. Chrome-tanned 
wax calf leather— Re-tanning. Intestinal leather — Parchment-like 
skin. Leather for organ pipes. 

Chapter VII 

IRON TANNAGE 214-224 

Research in iron tannage. 

Chapter VIII 
VEGETABLE-TANNED LIGHT LEATHERS .... 225-262 

Vegetable-tanned sheepskins — Quebracho tannage: Hemlock and 
quebracho tannage: Hemlock tannage: Combination tannage: 
Sumac tannage: Tanning with alum, sumac, and oak bark: Tanning 
with chestnut' extract: Tanning with sumac, alum, and salt: Que- 
bracho-tanned sheepskins. Skivers. Roller leather. Calfskin 
leather — Quebracho tannage: Gambier tannage: Dongola tannage. 
Velvet and suede leathers. Russia calf — Bleaching: Re-tanning with 
quebracho: Drumming with sumac. Vegetable-tanned kangaroo 



xii CONTENTS 

leather — Quebracho extract tannage: Gambier and sumac tannage: 
Other tannages. Vegetable-tanned side leather — Tanning with 
hemlock and quebracho extracts: Tanning with qucbracbo extract: 
Tanning with gambier, sumac, and oak extract: Tanning with 
gambier: Combination process: Pressing and splitting. Re-tanning 
with gambier and sumac — Re-tanning grains with sumac. Tanning 
sealskins — Levant grain: Walrus grain seal: Tanning the splits: 
Directions for finishing: Treatment for split linings. Tanning pig- 
skins — Tanning with sumac, oak bark, and alum. Tanning snake 
skins. Fancy leather calfskins. Combined vegetable and mineral 
tannage. Vegetable-tanned patent shoe tipping — Another re-tanning 
process. 

Chapter IX 
VEGETABLE-TANNED SOLE LEATHERS 263-291 

Rapid tanning processes. Oak leather. Non-acid hemlock tanning. 
Acid hemlock leather. Union leather — Extracting: bleaching. 
Rapid sole leather tannage — Tanning with chestnut extract. Drum 
tanning for sole and belting leathers. 



Chapter X • 
BELTING LEATHER 292-317 

Necessary characteristics. Leathers used in belting — Raw ma- 
terial. Manufacturing processes. Tanning agents. Practical con- 
siderations. Tanning of belting leather — Rockers: Handlers: Lay- 
aways: Bleaching: Oiling: Drying. Currying — Scouring: Skiving: 
Hand stuffing: Wheel stuffing: Hot stuffing: Stretching. 

Chapter XI 

STRAP, WELTING, BAG, CASE, AUTOMOBILE, AND 

HARNESS LEATHER 318-340 

Strap leather — Stock: Soaking: Depilating: Unhairing: Bating: 
Washing: Rockers or stick pits: Splitting: Layaways: Bleaching: 
Re-tanning: Stuffing: Setting: Tacking: Whitening and snuffing: 
Finishing. Goodyear welting — Tannage. Bag and case leathers — 
Tanning. Vegetable-tanned splits — Softening and stuffing, heavy 
splits: Stuffing for wax splits. Harness leather. Good color on 
heavily stuffed leather. Automobile leather — Tanning: Finishing. 

Chapter XII 
PATENT LEATHER 341-351 

Patent leather 1 — Linseed oil: Turpentine: Naphtha: Soluble or 
nitrated cotton: Lampblack: Chinese blue: Prussian blue: Umber: 
Litharge: Spirit black. Boiling the oil for the daub coat — Varnish: 
Application of compositions to leather. 



CONTENTS siii 

Chapter XIII 
DYEING LEATHER 352-418 

Classification of dyestuffs. Natural organic dyestuffs — Indigo: Log- 
wood: Brazil wood, peach wood, and Japan wood: Fustic: Osage 
orange: Cutch. Mineral dyestuffs. Artificial organic dyestuffs — 
Basic colors: Acid colors: Direct colors: Alizarine colors: Devel- 
oped colors. Dissolving dyestuffs. Preparatory treatment before 
dyeing vegetable-tanned skins. Dyeing vegetable-tanned leather — 
Brush dyeing: Tray dyeing: Drum dyeing: Paddle dyeing. Dyeing 
chrome-tanned leathers — Black on chrome leather: Dyes for 
chrome-tanned calfskins. Coloring alum-tanned leather. Methods 
of coloring chrome-tanned sheepskins — Coloring with acid dye- 
stuffs: Coloring with basic dyestuffs: Gambier mordant: Fustic or 
osage orange mordant: Sumac and titanium-potassium oxalate: 
Combined dyeing process: Dyeing light shades- with acid dyestuffs: 
Dyeing with direct colors: Acid colors and sodium bisulphate: 
Coloring with phosphine dyestuff: Fustic and logwood bottom: 
Sumac and acid color mordant: 'Practical formulas for popular 
shades: Coloring after fat-liquoring: Flesh-finished chrome sheep- 
skins: Coloring chrome-tanned sheepskins after fat-liquoring and 
drying out: Blacking with hematin and direct chrome black: Black- 

• ing with logwood and titanium-potassium oxalate: Blacking with 
direct chrome black. Methods of dyeing vegetable-tanned skins — 
Blacking vegetable-tanned skins: Dyeing with acid and basic dye- 
stuffs: Coloring with- artificial dyestuffs: Ox-blood shade: Brown 
shades: Dyeing with fancy effects: Marbled effects: Spray dyeing: 

• Antique leather: Bronze dyeings (dyeings with metallic luster). 
Coloring and finishing India-tanned skins — Washing: Re-tanning 
with sumac: Coloring the skins: Dyeing the skins black: Ooze 
leather. Coloring chamois leather. Dyeing chrome-tanned calf- 
skins blaok — 1. Dyeing with logwood and direct leather black: 
2. Dyeing with logwood, leather black' and titanium salt: 3. Dyeing 
with acid-blacks. Coloring chrome-tanned calfskins. Dyeing vege- 
table-tanned calfskins black — Logwood liquor: Dyeing with direct 
leather blacks. Coloring vegetable-tanned calfskins. Coloring 
velvet or suede leathers. Notes on ooze calf and Russia chrome 
leathers. Dyeing chrome-tanned goatskins — Dyeing with acid 
colors: Dyeing with basic colors: Sumac mordant for basic and 
acid dyes: Gambier mordant for tan shades: Process for tan and 
brown shades: Clearing the grain of grease: Dyeing with fustic 
extract and direct or anthracene colors: Use of tartar emetic. 
Notes and suggestions. Coloring with natural dyestuffs — Light 
tan shade: Dark tan shade: Ox-blood shade: Chocolate shade. 
Dyeing chrome-tanned goatskins black — Dyeing with hematin crys- 
tals or logwood and direct leather black: Dyeing with logwood, 
leather black, and titanium-potassium oxalate: Dyeing with chrome 
leather black: Another method of direct blacking: Blacking with 
logwood and iron liquor: Dyeing with logwood, potassium per- 
manganate, and iron liquor. Dyeing chrome kangaroo black — 
Yellow flesh and black grain. Chrome-tanned ooze calfskins. 
Chrome bag and belt leathers. Dyeing chrome side leather — Direct 



xiv CONTENTS 

dyeing with acid colors: Tannin mordant for basic dyestuffs: Red- 
brown shade. Dyeing chrome side leather black — Yellow leather. 
Coloring vegetable-tanned upper leather. Dyeing sealskins — Black- 
ing. Dyeing pigskins. Process for producing marbled suede, 
leather. Pigment finish — Mill coloring: The finish: Hand season- 
ing: Machine seasoning: Full grain finish. Blacking and stuffing 
chrome harness leather — Finishing. 

Chapter XIV 

FAT-LIQUORING 419-446 

Fat-liquoring process — Fat-liquors for chrome-tanned sheepskins: 
Fat-liquoring chrome-tanned calfskins. Oiling the leather. Fat- 
liquoring chrome-tanned kangaroo — Applying the fat-liquor. Fat- 
liquors for chrome side leather. Fat-liquoring vegetable-tanned 
side leathers — Fat-liquor formulas. Fat-liquoring vegetable-tanned 
calfskins — Sulphonated oils: Casein: Egg-yolk: Potash soaps: Fig 
soap. How to make and use sulphonated oils. Sulphonated oil 
on chrome leather. Sulphonated oil on vegetable-tanned leather. 
Sulphonated oil on sole leather. Castor-oil soap. Potash soap. 
Oiling chrome leather. Waterproof filling for sole leather. Stuffiing 
chrome lace leather. 

Chapter XV 

FINISHING LEATHER • . . . 447-500 

Setting-out: Drying: Dampening: Staking: Buffing: Tacking: Strip- 
ping: Seasoning: Rolling: Glazing: Ironing: Embossing: Boarding: 
Measuring: Sorting. Finishing chrome-tanned sheepskins — Black 
glazed finish: Seasoning for dull finish: Seasoning for colored 
sheepskins: Finish for embossed sheepskins: Finish for black 
embossed sheepskins: De-greasing sheepskins. Finish for India- 
tanned leather — Black glazed finish: Smooth dull finish: Finish for 
colored skins: Re-tanning with chrome liquor: Morocco finish: 
Crushed levant grain: Ooze or suede leather. Finishing skivers. 
Seasoning for chrome calfskins — Bright finish, smooth or boarded: 
Glazed finish: Seasoning for black-glazed finish: Boarded or box 
finish: Smooth dull finish: Seasoning for black dull finish: Gun-metal 
finish. Finishing chrome goat leather — Clearing the grain from 
grease: Blacking defective spots: Black glaze finish: Seasoning for 
colored leather: Dull finish. Finish for kangaroo leather. Finishing 
chrome side leather — Dull finish: Glazed finish: Boarded finish: 
Gun-metal finish: Storm-grain leather: Finish for colored leather: 
Heavy chrome grain leather: Black chrome oil grain leather: 
Leather for sporting goods. Finishing vegetable-tanned grains 
into black leather — Finish for bright boarded grain leather. Finish- 
ing rough leather. Finishing imperfect grains into patent tipping. 
Dressing for leather goods and furniture. Removing spots and 
stains from leather. Bright blacking varnish for shoe leather. 
A Waterproof leather dressing. A harness blacking. Blacking for 
vegetable-tanned leather. Sigs for greasy leather. Finishing splits 
— Chrome-tanned splits: Finish for the black: Soap black: Flour 



CONTENTS xv 

paste: Finishing splits into Goody ears, chair splits, etc.: Grain 
leather from splits. Materials used in finishing leather — Blood: 
Blood albumen: Egg albumen: Gelatine and glue: Gelatine: Glue: 
Isinglass: Casein: Irish moss: Algin: Shellac: Button lac: Pyroxylin. 

Chapter XVI 
WOOLSKINS AND FURS . . . 501-524 

Tanning woolskins — Soaking, washing and scouring: Liming: Tan- 
ning: Bleaching: De-greasing: Tanning with formaldehyde: Tan- 
ning with a mineral and vegetable tannage: Tanning with gambier: 
Tanning with alum, salt and hemlock extract: Coloring: Dyeing. 
Tanning furs and hair skins. Washmg greasy skins. Oil process. 
Oiling alum-tanned skins. Deodorizing furs and rugs — Cleaning 
furs: Liming. Chrome-tanned furs and woolskins. Tanning hair 
skins with alum and gambier. Cleaning white fur rugs— Bleaching 
skins with the hair on. Dyeing China goatskins black. Dyeing furs 
with acid colors — Re-tannage: Chlorinating the furs: Dyeing. Dye- 
ing with chromate colors. Dyeing furs black with furrol dyes — 
Preparation of the skins: 1. Drum killing with soda solution: 2. 
Drum killing with milk of lime: 3. Drum killing with caustic soda 
lye: 4. Brush killing with caustic soda lye: Mordanting the furs: 
Dyeing black: Raccoon (imitation skunk): Lambskins: Red-haired 
fox: Seal rabbit (English imitation of seal). Tanning for robes, 
coats, etc. — Alum and salt process: Softening and cleaning the 
stock. 

Chapter XVII 

VEGETABLE TANNING MATERIALS 525-557 

Grinding: Cone mill: Disc chipper: Secondary reduction. Leaching 
— Sprinkler leaches: Autoclave system. Clarification. Concentra- 
tion. Chestnut wood. Oak wood. Barks — Chestnut bark: Oak 
bark: Hemlock bark. Quebracho. Valonia. Mangrove bark. Gall 
nuts. Sumac (rhus coriaria) — Mascolino: Rhus Glabra: Rhus 
Typhina. Gambier. Myrabolans. Divi-divi. Algarrobilla. Mimosa 
bark. Wattle bark. Palmetto. Sulphite cellulose extract. 

Chapter XVIII 
SYNTHETIC TANNING MATERIALS 558-566 

Chapter XIX 
UNUSUAL TANNING PROCESSES 567-577 

Electric tanning. Vacuum tanning. Seymour- Jones method. 
Organ leather. Leather for player-pianos — Pneumatic pouches: 
Substitutes. Shark-skin leather — Catching and handling: Treatment 
of skins. Porpoise leather. 



xvi CONTENTS 

Chapter XX 

ARTIFICIAL LEATHER, DOPE SPLITS, AND 

PYROXYLIN FINISHES 578-584 

Pyroxylin — Solvents: Procedure: Acid formula. Coating real 
leather. 

Chapter XXI 

ANALYTICAL METHODS 585-664 

Water analysis — Total solids: Ash: Organic matter: Sulphates: 
Chlorides: Iron: Temporary hardness: Permanent hardness: Mag- 
nesia hardness: Free carbonic acid: Alkaline carbonates. Soaks 
— Stiasny's method. Lime — Available lime: Iron, calcium, and mag- 
nesium: Alkalinity of saturated solution. Sodium sulphide — 
Na 2 S.9H 2 0: Total alkalinity and NaOH in the Na 2 S. Analysis of 
arsenic sulphide — Arsenic: Sulphide sulphur (Procter's method). 
Lime liquors — Soluble lime and hide substance: Available lime and 
CaC0 3 : Hide substance continued: Kjeldahl method for hide sub- 
stance. Sulphide lime liquors — Sodium sulphide: Soluble lime and 
hide substance: Available lime and CaCOs. De-liming test. Salt 
— Calcium oxide (CaO): Sulphates (SO s ). Aluminum sulphate — 
Aluminum oxide (A1 2 3 ) : Total sulphuric acid (H2SO1): Free 
sulphuric acid (H2SO4) : Ferric oxide (Fe^0 3 ). Pickle — Sulphuric 
acid: Sodium chloride. Formaldehyde — Romijn's method. Two- 
bath chrome liquors — Determination of Cr as Cr 2 3 , Na 2 Cr 2 7 , or 
NaaCrd: Acidity: (a) Assume bath is all Na 2 Cr 2 7 : Strength: (b) 
Assume bath is a mixture of Na 2 Cr 2 7 and Na 2 Cr0 4 : Strength: 

(c) Assume bath is all H 2 Cr 2 7 : Strength: (d) Assume bath is a 
mixture of H 2 Cr 2 7 and Na 2 Cr 2 07: Strength: (e) When bath con- 
tains free acid (HC1 or H 2 S0 4 ) : Strength: Na 2 S 2 3 in hypo bath: 
Second bath when made up of NaHSOs. One-bath chrome liquor 
— 1. Determination of chromium: (a) Determination of Cr in new 
or spent liquor: Strength: (b) Determination of Cr in stock liquor: 
Strength: (c) Determination of basicity for diluted chrome liquors: 

(d) Determination of basicity of stock liquor: Strength: 2. Use of 
above results to obtain correct basicity of one-bath chrome liquors: 

(a) Assume the analysis shows the ratio to be 52:83.2: Surama r y: 

(b) Assume the ratio is below 80, say 69:16: Summary. Vegetable 
tanning materials — Unextracted materials: Extracts: Tan liquors. 
Official method of the American Leather Chemists' Association for 
the analysis of vegetable materials containing tannin. I. Raw and 
spent materials — (1) Caution: (2) Preparation of sample: (3) Water 
determination: (4) Amount of sample to be extracted: (5) Extrac- 
tion: (6) Analysis. II. Analysis of extract — (7) Amount and di- 
lution for analysis: (8) Total solids: (9) Water: (10) Soluble 
solids: (11) Insolubles: (12) Non-tannins: (13) Tannin. III. Analy- 
sis of liquor — (14) Dilution: (15) Total solids: (16) Soluble solids: 
(17) Insolubles: (18) Non-tannins. IV. Temperature, evaporation 
and drying, dishes — (19) Temperature, (20) Evaporation: (21) 
Dishes. V. Determination of total acidity of liquors — (22) Re- 
agents. VI. General. Official method for sampling tanning materials 



CONTENTS xvh 



—General- (1) Solid, powdered and pasty extracts: (2) Liquid- ex- 
tractni barrels: (3) Liquid extract in bulk: (4) Liquid extract m 
ank-cars: (5) Crude tanning materials (6) Spent materials from 
1 u c n\ Tormina- liauors. Official method tor analysis oi 
^ble-^ S^ Q ?1) Preparation of sample: (2) Moisture: 
H) Fats: (4) Ash: (5) Water-soluble material: (6) Glucose solu- 
ions-Copper sulphate: Alkaline tartrate *°^J£?^ 
acetate solution. Determination. Munson and Walker s table 
( N Log en. Reagents-Standard acid solutions: Standard alkali 
o Lion: Sulphuric acid: Sodium hydroxide solution: Jotassium 
sulphate: Indicator. Determination. Chrome-tanned l^'-**; 
Free sulphur: Ash: Chromium: Complete analysis: Water: Ash. 
Chromium and aluminum: Fat and sulphur. Water solubles- 
TarTns- Sugar: Sulphates: Chlorides: Barium. Water msolubles 
-Sulphates- Barium and lead: Alkaline salts: Total so luble sul- 
phats Alkaline sulphates: Hide substance. Provisional method 
for the analysis of chrome leather-Chrome determination. Pro- 
visional method for sulphonated oils-Moisture: Ash: Non-sapom- 
fiable Combined SO s : Total fatty oil. Provisional method for 
anaWsis of moellons-Moisture: Ash: Unsapomfiable: Oxidized 
f£tv acids- Free fatty acids. Provisional method for analysis of 
hard grea es-Titer twt; Unsaponifiable: Free fatty acids., Provi- 
sional method for analysis of lactic acid-Free sulphuric acid: 
VoStile acid. Table showing the relation of amounts of volatile 
acid found in distillate obtained under standard conditions to the 
amounts actually present in distilling flask in *f^^°™ 
distillation: Two distillations: Free acid and anhydude Official 
form for report on extract analysis. Sulphuric acid in leather- 
Procter and Searle method: Balland and Maljean method: Jeans 
method Soap analysis-Water: Fatty acids: Total alkali: Insoluble 
S alcohol: Free sodium hydroxide: Free oil. Oils. (A) Lubricating 
oil-Soap: Rosin oil: Saponifiable oil (qualitative test): Unsapom- 
fiables: Specific gravity: Cold test: Cloud test: Viscosity: Total 
acidity Mineral acids: Flash-point: Burning point: Loss on evap- 
oration and tendency to gum: Suspended matter: Anti-fluorescents. 
(B) Oil numbers for other than petroleum and lubricating oils- 
odine number: Method: Helmer number: Reichert Meissl number: 
Maumene number: Acetyl number: Titer test: Acid number: E ster 
number: Polenske number. Analysis of titanium-potassium oxalate 
OTiCu)-Aluminum: Iron and titanium: Oxalate: Ash: Potassium. 
Analysis of blood albumen-Water: Ash: Inso uble matter: Non- 
albumen. Analysis of formic acid-Total acidity : Acetic acid 
Mineral acids. Analysis of egg-yolk-Water : Ash Fat. Salt 
Nitrogen or albumen. Analysis of acetate of iron liquor-Total 
acidity: Iron oxide: Ash: Sulphuric acid: Acetic acid. Some simple 
chemical tests for leather makers-Lime: Linseed meal (crushed 
linseed): Dried blood: Gum arabic: Dyes: Cod-liver oil: Glucose. 
Salt: Ammonium chloride (sal ammoniac): Caustic soda: Ferrous 
sulphate (green vitriol): Sodium thiosulphate (hypo): Flour: Egg- 
yolk- Ammonia or ammonium hydroxide: Borax Mineral acids: 
Shellac: Soda: Carbolic acid or phenol: Sumac: Lactic acid: Soaps: 
Indicators. 



xviii CONTENTS 

Chapter XXII 
DISPOSAL OF TANNERY WASTE 665-669 

Classification and nature of tannery wastes; Plain sedimentation: 
Mechanical sedimentation: Activated sludge process: Other methods 
of treatment. 

Chapter XXIII 
USEFUL DATA 670-682 

Thermometer conversions. Boiling and freezing points of ther- 
mometers. Comparison of thermometers. Specific gravity, degrees 
Twaddell, barkometer and Baume. Weight and specific gravity of 
liquids — Water. Weights and measures — Troy weight: Apothe- 
caries' weight: Avoirdupois weight: Dry measure: Liquid measure: 
Long measure: Cloth measure: Square measure: Surveyor's meas- 
ure: Cubic measure. Metric equivalents — Linear measure: Square 
measure: Weights: Volume: Capacity: Multiples for conversion of 
quantities: Multiples for conversion of distances: Multiples for 
conversion of capacities. Approximate metric equivalents. Ca- 
pacities of vats in gallons for each inch in depth — Circular in form: 
Square in form. Sundry calculations — Volume of a cube: Volume 
of a parallelopipedon: Volume of a cylinder: Volume of a cone: 
Volume of a frustum of a cone: Volume of a sphere: Diameter and 
speed of pulleys. Heat, steam, evaporation and electricity. Evapo- 
ration in vacuum. Boiling point of water at reduced pressure. 
Temperature of steam at various pressures. 

GLOSSARY OF TERMS USED IN TANNING AND RE- 
LATED INDUSTRIES 683-687 



LIST OF ILLUSTRATIONS 

FIGURE PAGE 

1.— Skinning the head and cheek. The knife should pass 
along the hide, starting at the base of the right horn 
and extending across to the left horn, and then 

down through the left nostril 4 

2. — Skinning the forelegs 5 

3. — Skinning the side 5 

4.— Skinning the hind legs to make a uniform pattern . 6 

5. — Skinning the buttocks 6 

6. — Skinning the rump 

7. — Skinning the back 7 

8. — Beating the fell over the rump and round .... 8 

9. — Skinning the neck 8 

10.— Dotted lines show ripping-open cuts necessary to pro- 
duce a hide of good pattern 

11. — Dotted lines indicate proper cuts in skinning the head 10 

12. — A hide of good pattern and trim 11 

13. — How to fold a hide • * 2 

14. — Checking off a load of hides 13 

15.—A hide cellar 14 

16._Cowhide, showing character of grain 16 

17 —Calfskin, showing grain on finished leather ... 20 
18. — Horsehide, showing character of grain .... 21 
19. — Goatskin, showing grain on finished leather ... 22 
20.— Warehouse in a goatskin tannery; stock being re- 
ceived and weighed 24 

21. — Raw stock. Goatskins come from all parts of the 
world. They arrive in a dry condition and before 

tanning are sorted into various grades and weights 24 

22. — Hogskin, showing characteristic grain 29 

23. — Skinning out the legs of a sheep 30 

24. — Skinning over the flank of a sheep 31 

25.— Stripping-off over the back of a sheep .... 32 

26. — Fisting off a sheepskin 33 

27. — Sheepskin, showing characteristic grain .... 34 

28.— Lambskin 35 

xix 



xx LIST OF ILLUSTRATIONS 

FIGURE PAGE 

29.— Kid skin 35 

30. — Kangaroo skin 35 

31. — Human skin 36 

32. — Sealskin 36 

33. — Alligator skin . 36 

34. — Cross-section of calfskin 49 

35. — Cross-section of cowhide 50 

36. — Cross-section of calfskin 51 

37. — Pin-mill, wash-wheel, or drum for washing fresh 

hides 56 

38. — Washing hides preparatory to soaking 57 

39. — Fulling stocks 59 

40. — Turner pneumatic fleshing machine 60 

41. — Hides ready for depilation 61 

42. — Lime plunger 79 

43.— Beam knife 80 

44. — Whitney model "S" unhairing machine .... 80 

45.— Broad flesher 81 

46. — Spring style fleshing knife 81 

47.— Monitor flesher 81 

48. — Automatic roller fleshing machine 82 

49. — Unhairing on the Leidgen machine 93 

50. — Hand fleshing on the beam 94 

51. — Inspection for fine hairs 95 

52. — Checking machine, used for splitting necks on calf- 
skins ' 99 

53. — A typical beam-house of a goatskin tannery . .-■ . 100 

54.— Fleshing 108 

55. — Bate beam-stone 117 

56. — Belt-knife splitting machine 131 

57. — Rubber roll putting-out machine 132 

58. — Buffing machine, used for snuffing grain for ooze, 

and flesh for suede leather 146 

59.— Buffing wheel 148 

60.— Knee-staker ,150 

61. — Tan-room in a goatskin tannery. The operation is 

carried out either in paddle or drum as shown . . 162 
62. — Line of shaving machines used for producing a 

smooth effect on the flesh side 163 



LIST OF ILLUSTRATIONS xxi 

FIGURE PAGE 

63. — Shaving machine 164 

64. — Slicker and handle 232 

65.— Moon-knife . . . 232 

66. — Union splitter. Formerly much used for furniture 
and automobile leather, but now replaced by band- 
knife machine 246 

67. — Iron frame stoning- jack 249 

68. — Cork arm-board 255 

69. — Sole leather rolling- jack 268 

70. — Mechanical transfer in the tan-yard, showing pack 

going to rocker 272 

71. — Mechanical hoist for moving hides 273 

72. — View in the tan-yard, showing series of layers . . 274 

73. — Cropping 275 

74. — Cropped hides and bellies ready for final layer . . 276 

75. — Quirin press or wringer 277 

76. — Extract wheels 278 

77.— Ready for the bleach 279 

78. — Hides suspended in the bleach 280 

79. — Bleaching machine . . . 281 

80. — Placing in loading wheel 282 

81. — Removing from loading wheel . . . . . . . 283 

82. — Setting-out after tempering ... 284 

83.— Rolling- jacks 285 

84. — Drying-loft 286 

85. — Applying the bright finish to sole leather .... 287 

86. — Brushing machine for sole leather 288 

87.— Currier's knife 308 

88. — Whitening machine, used for cleaning-up flesh side 

of various kinds of leather 309 

89. — Serial table setting-out machine 313 

90. — Heavy rolling-jack . . ; . . . . . . . 316 

9.1. — Boarding machine •. . . 325 

' 92. — Sheridan embossing press 337 

93. — Embossing machine 338 

94. — Turner hydraulic embossing and smooth-plate press 339 

95. — Coloring goatskins 357 

96. — Top pan blacking machine used for seasoning and 

coloring . . . . . 386 



xxii LIST OF ILLUSTRATIONS 

FIGURE PAGE 

97. — Exterior view of Proctor dryer 447 

98. — Skins entering at the "wet end" of Proctor dryer . 448 

99. — Skins leaving the "dry end" of Proctor dryer . . . 449 
100. — Interior of a typical dry-room in a goatskin tannery. 

The room is heated by steam pipes on the floor and 

ventilated by means of fans 450 

101. — Side view of Sturtevant dryer showing supply pipe, 

heater and open tube 451 

102. — Rear end of heaters, Sturtevant dryer, showing steam 

and drip connections 452 

103. — Sturtevant leather dryer, double tube, showing drying 

trucks 453 

104. — End of two tubes of Sturtevant dryer, showing skins 

hanging from chain belt-conveyor 454 

105. — Looking into the end of Sturtevant leather dryer, 

showing skins on conveyor 455 

106. — Standard staking machine . ;. . . ... . 456 

107. — Staking, or softening and stretching the damp stock 457 

108. — Perching goatskins, sometimes termed re-staking . 458 

109. — Buffing room in a goatskin tannery 459 

110. — Bower glazing machine 460 

111. — Flat bed glazing machine 461 

112. — A line of glazing-jacks for producing a bright finish 

on glazed kid 462 

113. — Segment measuring machine 463 

114. — Sorting finished skins 464 

115. — Eureka bark mill 527 

116. — Chestnut trees; giants of the forest 538 

117. — A flume on the chestnut wood operations .... 539 

118. — Flume terminus for chestnut wood 540 

119. — Carting quebracho logs to port of shipment; trees 

in the background 548 

120. — Hauling in netted sharks 574 

121.- — Roping a shark 575 

122. — Landing a shark. Note skins on pier 575 

123. — Tea's extractor 613 

124. — Combined evaporator and dryer ....... 619 



ACKNOWLEDGMENTS 

The illustrations appearing in this book have been kindly 
furnished by the following firms and Government Depart- 
ment : 

Goatskin Tanning 

Dungan, Hood & Co., Inc., Philadelphia, Pa. 

Sole Leather Tanning 

J. H. Ladew Co., Newark, N. J. 

Chestnut Extract 

Champion Fibre Co., Canton, N. C. 

Quebracho Wood 

A. Klipstein & Co., New York City 

Leather Dryers 

Proctor & Schwartz, Philadelphia, Pa. 

B. F. Sturtevant & Co., Boston, Mass. 

Skins and Hides 

Bureau of Chemistry, U. S. Dept. of Agriculture, Wash- 
ington, D. C. 

Cross Section of Calfskin 

Dr. George D. Rosenthal, New York City 

Flaying 

Farmers' Bulletin 1055, U. S. Dept. of Agriculture, Wash- 
ington, D. C. 

Tanning Machinery 

Turner Tanning Machinery Co., Peabody, Mass. 
G. W. Baker Machine Co., Wilmington, Del. 
T. W. & C. B. Sheridan Co., New York City 
Whitney Machine Co., Winchester, Mass. 



xxm 



INTRODUCTION 

In presenting any book on a special subject it is customary 
to commence with the history of that subject, and by gradual 
stages bring it down to the present time. In attempting to do 
this, the author encountered so many difficulties and so many 
unauthentic, conflicting records that he gave it up as being 
too uncertain. If, however, any dependence can be placed 
upon the records of Scripture, we must conclude that the 
manufacture of leather is the oldest of the industries, for in 
Genesis III, 21, we read, "Unto Adam also and to his wife 
did the Lord God make coats of skins and clothed them." 

It is interesting to know that the first method for preserv- 
ing hide and skin in a more or less pliable and imputrescible 
condition probably consisted in treating the pelt with the 
grease and brains of the animal itself, which were worked in 
by a process of pounding and stretching. Following this 
primitive method came the smoke treatment, then the appli- 
cation of salts containing alum. The dyeing of this leather 
no doubt led to the discovery of a few vegetable tanning ma- 
terials. It remained, however, for the last fifty years to see 
more done for the advancement of the industry than ever be- 
fore, and in this wonderful development America has played 
no small part. 



PRACTICAL TANNING 



CHAPTER I 
HIDES AND SKINS 

The hides and skins used in the manufacture of leather 
are generally obtained from animals killed for food. The 
coverings of large animals are classified as hides, whereas 
those of small animals are known as skins. The production 
of hides and skins in the United States during 1920 amounted 
to 894,000,000 lb., green basis, when 1 lb. of dry hide equals 
2 lb. of green hide. Hides and skins soon putrefy if allowed 
to remain in a moist condition, so it becomes necessary to 
treat them in such a manner that they may be kept undam- 
aged until ready for the tanning processes. This operation, 
known as curing, may be done in several ways, each one being 
more or less peculiar to the locality from which the hides are 
shipped. The cure has a decided influence upon the hide, and 
largely determines the character of the leather. 

Classification of pelts. — The pelts of animals come to the 
tanner in four conditions: (1) green (fresh from the ani- 
mal) ; (2) green-salted (where the salt has been rubbed on the 
flesh side) ; (3) dry-salted (rubbed with salt and dried) ; and 
(4) dried (usually stretched on boards in the sun). The pelts 
so received are divided according to size into three general 
classes, namely: hides, kips, and skins: Hides comprise pelts 
from large and fully grown animals such as the cow, horse, 
camel and walrus. These give thick, heavy leather for shoe 
soles, machinery belting, harness, and other purposes where 
stiffness and strength, combined with wearing qualities, are 
necessary. They are also cut into splits for use as shoe uppers, 
and bag, case, strap, automobile, carriage, furniture, and up- 
holstering leathers. Kips are the skins of undersized animals 
of the above species. Skins are obtained from small animals 
such as calves, sheep, and goats. Kips and skins yield a 
lighter leather than hides, which is suitable for a great variety 

1 



PRACTICAL TANNING 



of purposes such as uppers for shoes, pocketbooks, bookbind- 
ing, gloves, and fancy leather. Pelts vary in thickness and 
texture in different parts, being thicker on the neck and butt 
than on the flank and belly. Pelts of the same species vary 
greatly according to the climatic conditions under which the 
animals are raised, also their breeding and feed. They often 
show injuries like cuts, brand-marks, grub-holes, and sores 
caused by the bot-fly or warble. Diseased hides are some- 
times found, and are a source of great danger to the tanner 
on account of the contagious nature of some of the diseases, 
especially anthrax. 

Dry or flint hides. — The simplest form of cure consists in 
drying the hides in the open where they are exposed to the 
action of both sun and wind, a method commonly adopted in 
most tropical countries. Although curing by this method has 
the advantage of simplicity, it has disadvantages owing to 
the condition of the hide substance. Too rapid drying results 
in the contraction and hardening of the surface, and the mois- 
ture, not being removed from the middle section, gives rise 
to bacterial action deleterious to the hide substance. As the 
damage thus caused can only be detected in the beam-house, 
it is apparent that the practice should be discouraged. The 
temperature at which hides are dried is of great importance. 
The best conditions are a comparatively low temperature and 
good circulation of air. The higher the temperature, the 
harder the stock and the slower it will wet back in the soaks. 

Dry-salted hides. — These differ from flint hides in that a 
coating of salt has been applied to the flesh side, and, after re- 
maining in packs for some time, they are spread out and al- 
lowed to dry in the sun. Dry-salted hides have the advantage 
over dry hides in that they do not contract during the dry- 
ing and are much more readily softened in the soaks. 

Green-salted hides. — The stock coming to the tanner in 
this condition has been salted on the flesh with common salt 
and placed in piles to cure. The hides are piled-down in such 
a manner that the slope is toward the center. In this way the 
brine formed is retained and the cure materially aided. The 



HIDES AND SKINS 3 

time necessary for a thorough cure is at least thirty days. The 
hides are taken-up, and, after the salt has been partly removed 
from them, they are folded into a bundle for shipment. 

Salt stains. — In salting hides it is sometimes found that 
iron, in the form of ferric chloride, is present. This iron 
becomes deposited in the hide, and shows up during the tan- 
ning as black spots known as salt stains. Clots of blood or 
flesh are also likely to produce the same result. 

Packer hides. — The slaughtering of cattle on a large scale 
by the great packing-houses of the United States has resulted 
in a process so efficient that these hides are obtained in nearly 
as perfect a condition as their nature will permit. Thus the 
term "packer hide" has come to mean the best hide that can 
be bought. Skilled labor and attention to details have re- 
duced the possible damage to a minimum. 

Stuck-throats. — As the cattle arrive at the packing-house 
they are allowed to rest and cool off. The killing beds are 
usually arranged on the top floor of the building, and the cat- 
tle are driven up through runways or elevators. Two animals 
go into each knocking pen, there usually being half as many 
pens as skinning beds. A "knocker" uses a light sledge ham- 
mer, and strikes the animal a heavy blow on the forehead be- 
tween the eyes; if the animal does not drop immediately, a 
second blow is given. The skull is broken by this heavy blow 
and the animal becomes unconscious. The gate is now lifted, 
and by mechanical means the floor of the pen is raised to a 
sharp angle causing the carcass to slide to the sticking bed. The 
"sticker" inserts his knife vertically through the neck in such 
a way as not to tear the pattern of the hide, and when the 
knife has been entered sufficiently deep, it is turned crosswise 
to sever the jugular vein. The animal is now shackled by 
passing a chain around both hind legs, and the body raised 
from the floor, head down, in order to drain off the blood. 

Cut-throats. — When animals are killed "kosher," accord- 
ing to the Rabbinical law, the steer is not knocked senseless, 
but is shackled by the hind legs and raised to such a position 
that the head just rests on the floor. By means of a muzzle 



4 PRACTICAL TANNING 

the head is turned back and the throat washed to remove grit. 
The Rabbi blesses the animal and with a long knife makes 
one downward cut back of the jaw, almost severing the head 
from the spinal column. 

Flaying. — Whether the animal is a stuck-throat or cut- 
throat, the operation of flaying is similar in each case. In the 




Figure 1. — Skinning the head and cheek. The knife should pass 
along the hide, starting at the base of the right horn and 
extending across to the left horn, and then down through 
the left nostril. 

large packing-houses, skinning is done by several men, each 
performing a specific part of the operation. The "header" 
sticks his knife in at the top of the head and makes a cut 
across the left side of the animal's face, continuing downward 
along the left side through the nostril. The cheeks are skinned 
out (figure 1), and the under side opened from the sticking 
cut through the center of the lower lip. This method leaves 
the pate on the right side of the hide, and allows it to lie flat 
when placed in the pack. The carcass is next lowered to the 



HIDES AND SKINS 




Figure 2.— Skinning the forelegs, 
floor where it is laid on the back and held in position by a 
pritch pole. The claws and feet are removed by the "legger" 
(figure 2) and the sweetbreads are taken out. In skinning the 
front legs the cut is upward on the right side and toward the 
center of the knee. The same holds good of the hind legs, 




Figure 3.— Skinning the side. 



PRACTICAL TANNING 




Figure 4. — Skinning the hind legs to make a uniform pattern. 




Figure 5. — Skinning the buttocks. 



HIDES AND SKINS 




Figure 6. — Skinning the rump. 




Figure 7. — Skinning the back. 



PRACTICAL TANNING 




Figure 8. — Beating the fell over the rump and round. 




Figure 9. — Skinning the neck. 



HIDES AND SKINS 9 

except that the cut runs toward the center. The "ripper-open" 
next follows, opening the steer along the belly (figure 3) from 
the sticking cut to the tail. The "floorsman" or "sider" now 
removes the hide from the belly (figure 4) and cuts along the 
brisket and back to the inside of the hind leg (figure 5) close 
to the tail. After cutting down the side of the animal he 
makes the cut at the brisket and foreleg to joint, and, on the 




Figure 10. — Dotted lines show ripping-open cuts 
necessary to produce a hide of good pattern. 



hind leg (figure 6), he connects with the hind-legger cut. The 
hide is now carefully removed from the belly and down the 
sides. The body is then lifted until only the forward quarter 
remains on the floor, and the "tail-puller" pulls the hide off 
the tail. The "rumper" (figure 7) cuts the hide away from the 
base of the tail and rump. The body is again raised, and the 
"fell cutter" removes the hide from the hind legs and "round." 
The fell puller takes the hind shanks and pulls, while the "fell 
beater" (figure 8) pounds away the hide by means of the back 



10 PRACTICAL TANNING 

edge of cleavers. The "backer" (figure 9) finishes the flaying 
by removing the hide from the shoulders. Figures 10 and 1 1 
show cuts required during skinning, while figure 12 shows a 
hide of good pattern. 

Curing. — As the hide drops from the carcass it is spread 
on the floor and inspected for cuts, scores, grubs, and other 
imperfections. It is then thrown into a chute leading to the 




Figure 11. — Dotted lines indicate proper cuts in 
skinning the head. 

hide cellar. Here the hides are assorted into different grades, 
classes and weights, each grade being assembled in its respec- 
tive pack. The workmen in the hide cellar are usually about 
two hours behind the killing gang, so that the animal heat may 
be out of the hides before salting. As the cellar gang receive 
the hides, they split the ears and then pile them down flat with 
flesh side up. Over each hide is sprinkled about 40 pounds of 
rock salt, and the outside hides in the pack are turned over 
so as to retain the pickle in the stock and hold the pile in 



HIDES AND SKINS 



11 



shape. The piles are low and fiat to prevent drying out. After 
the back edge and corners are put in, the sides are built up. 
When the back and sides have been made, the spreads are put 
This is done in such a manner that the heads come into 



in 



the center of the pack. As the spreads are placed in, the front 
is built up. Hides packed in the proper way will keep for one 
or two years, but in practice they are never left for this length 




Figure 12. — A hide of good pattern and trim. 



of time, thirty days being the usual period. The danger of 
standing too long is indicated by salt stains, but these may be 
prevented by adding "cyco" powder to the salt. This powder 
consists essentially of sodium bisulphite, and is sold under 
the above trade name. 

In putting down hides, the work is done by a gang consist- 
ing of two spreaders, one salt thrower, and a salt trucker, who 
should handle about 40 hides an hour. To obtain the best 
results, the cellars should be kept at as even a temperature as 



12 



PRACTICAL TANNING 



possible, which should not vary greatly from 65 degrees 
Fahrenheit. 

Taking-up hides. — In taking-np a pack of hides, the repre- 
sentatives of buyer and seller are present. As the hides come 



\ 










\r 



Figure 13. — How to fold a hide: (a) first step; (b) second step; (c) 
third step. The shading represents the hair side. 

from the pack they are shaken and drawn over a "heaver" 
(a kind of horse) to remove excess salt. They are then spread 
on the floor, hair side up, and inspected for hairslips, manure, 
and brands. They are next turned flesh side up and swept 
free from adhering salt. Another inspection is made for cuts, 



HIDES AND SKINS 13 

scores, and grubs, after which they are sorted according to 
grade, and classified as firsts and seconds, brands, cows, and 
steers. The No. 1 hides are rolled up with hair out, and the 
No. 2 with flesh out. After rolling (figure 13), they are tied, 
weighed, and further classified as heavy, spready, medium, 
light, and extreme. 

Sweep tare. — In taking-up hides a tare allowance is made, 





kIET'' 










51\j i 










%?• •'" 1 




v;f!. "" 




a.*^ 


,1 U-«: % 










; 




^^^^^fi. 


■ 


V i 










g^BM 


|l 




%«&m» 





Figure 14. — Checking off a load of hides. 

determined by what is known as the sweep tare. Ten hides 
are selected at random, weighed, swept thoroughly both on 
flesh and hair sides, and weighed again. The loss in weight 
is then taken for the whole pack. If this tare is not satisfac- 
tory to either buyer or seller, another lot of 10 hides is taken, 
and the average loss on the 20 hides indicates the tare allow- 
ance. Since the time of year has some influence on the tare 
allowance, it is usually determined before the hides are taken- 
up. For instance, July hides, on account of short hair, are 
given an allowance of I to 1$ lb., whereas March hides, hav- 
ing long hair, are given an allowance of 2 to 2\ lb. Figure 
14 shows hides arriving at a tannery, and figure 15 depicts 
a typical hide cellar. 



14 



PRACTICAL TANNING 



Grubs. — Among the defects found in hides, note should be 
made of the damage caused by the "bot-fly" or "warble fly" 
(hypoderma bovis). The grub deposits eggs in the animal; 
but just how, is open to controversy. Observations by work- 
ers in the Department of Agriculture, Bureau of Animal In- 
dustry, both of the United States and Canada, indicate con- 
clusively that the eggs are deposited in the hair while the ani- 




Figure 15. — A hide cellar. 

mal is in a reclining position. According to a report of Dr. 
Seymour Hardwin, he observed a fly on the ground near a 
recumbent cow. It ran backwards, reached upward from the 
ground, and oviposited on the hair hanging down around the 
coronet. On another occasion a fly on the ground ran back- 
ward in the same manner, and oviposited about six inches 
below the point of the ischium, where the cow's body came in 
contact with the ground. From this point it laid eggs at in- 
tervals all along the side near the ground, as far forward as 
the elbow, without touching the animal except with the ovi- 



HIDES AND SKINS 15 

positor. This journey took some time, as the fly rested one 
or two minutes after ovipositing. With regard to irritation, 
Dr. Hardwin observed that while the animal was recumbent 
no annoyance was apparent, probably because the fly was on 
the ground, but when standing it was a different matter, as the 
fly was forced to grasp the hair while ovipositing. 

An extended series of experiments have shown conclusively 
that the larvae enter the animal both through the skin and by 
the mouth. In either case, the parasite travels along a pretty 
definite route, passing down the gullet to the diaphragm, and 
then through connective tissue along the sides and vertebrae 
to the back. The larvae found in the oesophagus, spinal canal, 
and subcutaneous tissue all had about the same dimensions. 
Signs of their migration through the intervening tissue were 
also found, proving that the process is continuous. On reach- 
ing the back, the larvae develop, and here force their way 
through the hide, first causing a swelling during their pupal 
stage, and finally making a puncture, falling, an undeveloped 
grub, to the ground where it matures. 

In small numbers, warble flies do little injury to the health 
of the animal, although cases are on record where an excessive 
number of grubs have caused death. The holes produced by 
the grub soon heal, but if the animal is killed before the heal- 
ing is complete, they remain open and are a source of damage 
to the hide. Preventive measures are being taken in some 
States to overcome this nuisance, and it is hoped that they 
may become general practice. 

Hides from certain countries may be damaged by ticks, but 
the injury, however, appears only in the shanks, and is not so 
serious as that caused by grubs. 

Grub allowance. — The grubbing of native steers is per- 
mitted and a grub allowance made between January 1 and 
June 1. This is done by sampling. The hides selected for 
grubbing, twenty in number, are spread on the floor, and the 
purchaser's agent, by means of a spade, finds as many grubs 
as possible. When all grubs have been found to a limit of 
five, another hide is examined, and so on. If the number of 



16 



PRACTICAL TANNING 



grubs found is not satisfactory to either buyer or seller, an- 
other 20 hides are taken, and the grub allowance based on the 
40 hides so chosen. 

Hide selections. — When purchasing hides, the buyer looks 
for certain selections, depending on the kind of leather he is 




Figure 16. — Cowhide, showing charac- 
ter of grain. 



producing and the market conditions. Figure 16 shows char- 
acteristic features of finished grain. 

Native steers. — Steer hides free from brands are graded 
according to weight as heavy hides, above 60 lb. ; light hides, 
between 50 and 60 lb. ; and extremes, between 35 and 50 
pounds. 

Heavy hides are usually kept separate and sold for belting 
leather. Light hides sell for one cent less per pound, and ex- 
tremes for two cents less, than heavy hides. Kosher hides 
are included in regular lots, and are sold for \ cent reduction. 

Spready hides. — Native steers going into this selection 
must be perfect in all respects, free from brands and grubs. 
In the Western States the measurement of a spready hide 
must be 6 feet 6 inches across the shoulders just back of the 
brisket, whereas in the East the measurement is 6 feet 8 
inches. Hides of this class are used largely for furniture and 
automobile upholstery. As winter-killed hides are likely to 



HIDES AND SKINS 17 

be very grubby, the tanner prefers to purchase stock killed 
from June to January. These hides bring the top prices today, 
while several years ago they went at lower figures than other 
stock. 

Spready native cows must be perfect and measure 6 feet 4 
inches across the brisket, and go into the same trade as spready 
steers. 

Texas steers. — These hides are from branded range cat- 
tle, and on account of their plump condition find a ready mar- 
ket in the sole-leather trade. The cattle themselves, however, 
are underfed, and are known at the stockyards as "bone cret- 
er." Conditions, nevertheless, are changing, and the quality 
of the beef as well as of the hides is improving. Texas steers 
are butt-branded. The grubbing privilege extends from No- 
vember 1 to June 1. 

Colorado steers. — The hides from Colorado steers are side- 
branded either on one or both sides. As a rule they are more 
spready and have a more spongy feel than Texas hides. The 
grubbing privilege extends from December 1 to June 1. They 
are selected as heavies, over 60 lb.; lights, 50 to 60 lb., and 
extremes, 25 to 50 pounds. 

Cowhides. — The so-called native cowhides are free from 
brands, and are graded as heavies, over 55 lb., and lights, 
under 55 lb. Branded cows on the other hand are sold flat 
for weights. Both selections are grubbed from November 1 
to June 1, with the usual allowance of I cent off in case of 
kosher hides. 

Bull hides. — The hides known as native bulls are free from 
brands and stags. They are not grubbed and are usually 
sold flat. Branded bulls are also sold flat and not grubbed. 
' Bull hides are recognized by their tough pate, thick and ribby 
neck, and thin butt. As a rule, spready bulls are not sorted 
out. Some tanners, however, prefer selection, and in such 
cases the sorting is done by the broker. 

Country hides. — Green-salted hides not taken off by the 
large packers are known as country hides, but they may be 
from the same kind of cattle as those killed by the packers. 



18 PRACTICAL TANNING 

The principal difference is in the flaying, which is poorly or 
imperfectly done, the hides being badly cut, scored, and of 
poor pattern. These hides come from farmers or country 
butchers, who either salt them lightly or sell them green to 
small collectors, who in turn sell them either direct to the tan- 
ner, or, as is more often the case, to the large dealers. The 
latter sort the hides into different grades and weights, so that 
the tanner can obtain the selection desired. As a rule, the 
hides have been salted and re-salted several times, which im- 
parts to them a dark flesh color, with a consequent loss of 
hide substance. The defects of country hides include scores, 
grubs, hairslips, and poor patterns. Badly damaged hides are 
thrown into glue stock. 

Kips. — Hides from undersized animals or large calves are 
sold as kipskins, and range in weight from 15 to 25 lb. 
Branded or grubby skins go into seconds, and are sold at the 
proper reduction. 

South American hides. — River Plate hides, or "straight 
hides" as they are known in the trade, come from South and 
Central America. These are dry hides shipped from Argen- 
tina and Uruguay, and are spoken of as "Buenos Aires" and 
"Montevideos," taking their name from the point of shipment. 
These hides are from range cattle and are considered the best 
dry hides on the market. Other hides also take their names 
from the point of shipment and are known as "Puerto Cabel- 
los," "Maracaibos," "Caracas," "Costa Ricas," "Central 
Americas," and "Orinocos." They vary in character as to 
plumpness and quality of grain. Salted hides imported from 
South America come in as "frigorificos," "saladeros," and 
"metaderos." Frigorificos are hides from animals the meat 
of which is shipped from Argentina as frozen beef; saladeros 
are from the smaller packing-houses of Argentina and Uru- 
guay; while metaderos are hides from the village butcher and 
correspond to American country hides. Other dry hides come 
into this market from China and India. 

Anglo-American hides. — These are hides taken from cat- 
tle shipped to England on the hoof. They have all of the 



HIDES AND SKINS 19 

characteristics of packer hides, except that they have a short 
shank, and so bring a somewhat better price than packer hides. 
Swiss and Bavarian hides. — Hides coming from this 
source are in great demand for the manufacture of belting 
leather. The reason for this is that they are from animals 
. raised by peasants, who have given them the best of attention. 
They are plump and heavy, and have a very clear grain. 

Calfskins. — All skins under 15 lb., except slunks, are sold 
as calfskins. The following is the common classification: 

Slunk Weight, pounds 

No. 1 and 2 light deacons (country take-off) 7 down 

No. 1 and 2 heavy deacons (country take-off).... 7 to 8 

No. 1 and 2 light calf (butcher take-off) 7 to 8 

Calf 

No. 1 and 2 veal hair 8 to 15 

Kip (veal, 1st grade) 15 to 25 

Kip (grasser, 2nd quality) 15 to 25 

No. 1 and 2 runner kip (light kip, poor hair) 15 down 

No. 1 and 2 extreme cows (known as extra light) 25 to 45 

No. 1 and 2 buff or medium cows 45 to 60 

Cows 

No. 1 and 2 light steers 45 to 60 

No. 1 and 2 heavy steers 60 up 

No. 1 and 2 light bulls „ 45 to 60 

No. 1 and 2 medium bulls 60 to 85 

No. 1 and 2 heavy bulls „ 85 up 

No. 1 and 2 stags are classed with bulls. 

Trimmed calf and kip 

Calf 4 to 5 

Calf 5 to 7 

Calf 7 to 9 

Calf „ 9 to 12 

Kip 12 to 16 

Kip 16 to 20 

Figure 17 shows the grain on finished calfskin. 

Packer hides are thrown into seconds if they have one cut 
or five grubs. Country hides are thrown into seconds if they 
have one cut and one grub. A side or butt brand throws 
a hide into second grade. 

Horsehides. — These hides are obtained from domestic 
sources, and come mostly from work horses which have died 
in service. The best hides, however, are imported from 
France and Russia. These hides are sold by the piece ac- 



20 PRACTICAL TANNING 

cording to size and condition of the butt. The butts are 
cut off 21 inches from the tail, the cut being made clear across 
the hide. These butts are used for making the leather known 
as "cordovan," also for making a heavy leather worn in cold 
countries like northern Russia. The remaining portions of 
the hides, known as "fronts," are used for making shoe and 
glove leather, and are usually not tanned by the same firm 
handling the butts. No. 1 horsehides must be free from cuts, 
scores, brands, or dragged spots. Seconds are those having 




■> :f ' 



Figure 17. — Calfskin, showing grain on 
finished leather. 

these imperfections. There is also a difference between sum- 
mer and winter hides : In the summer, many horses die from 
exhaustion, and, as a rule, are not skinned promptly, some 
even lying several days in the street before removal. De- 
composition is going on all the time, and dragged spots occur. 
As the animal had been in imperfect health, this disturbance is 
reflected in the hide. Winter hides, on the other hand, are 
taken from animals killed after an accident, such as slipping 
on frozen pavements. The animals are in a healthy condition, 
and the hide is full of life and much stronger than summer 
hides, also much thicker. Even if the horse lies in the street, 
there is comparatively no putrefaction of the hide, which, 



HIDES AND SKINS 2I 

consequently, does not show dragged spot, Figure 18 shows 
rt* characteristic grain of finished leatheis. 

GoatsWns -These come chiefly from those eountr.es m 
Goatskins. ^ _ s nQt a popular 

s:i«^ p-r iy no th°o es " 

tic k ns ar available. We, therefore, depend upon the Or, 
tic skins «e America fof QUr raw mate _ 

e "ai an S d as m 'goatkins are tanned in the United States 
£ tan" olr Country, we have become the greatest im- 



■ ' 1 




Figure l8.-Horsehide, showing char- 
acter of gram. 

u ni«Tav«s have a few animals on their iarms. 
a Llr'thered by small collectors, who pass them on 

ri: arg r dealers. The dealer then brings them to the 
I kt place where they are bought by the big exporter, who 
Tn turn ships them to the United States or other countries . 
' The picking up and shipping of skins varies g-J^JJ 

ri^ZdeTwith skiL from an entirely different conn 
trv The climatic conditions of a region, of course, attect 
Z n Jure of the skin. Excessively wet or dry seasons have 



22 



PRACTICAL TANNING 



their influence upon the raw material, and in cold climates the 
skins take on a heavy growth of hair, while in warm climates 
the hair is short. The longer the hair, or the more closely the 
animal approaches the sheep, the poorer the pelt is for leather 
purposes. Figure 19 shows the natural grain on domestic 
goatskins. 

Curing. — Skins are cured in the same manner as hides, but 
inasmuch as they are thin and small, the details of the proc- 
ess are somewhat modified. The simplest method consists 




Figure 19. — Goatskin, showing grain 
on finished leather. 



of sun drying, where the skins are either spread out or hung 
up in the sun until dry. If the sun is too hot they are hung in 
the shade. Dry-salted skins are given an application of salt, 
and then dried in the sun or shade. Wet-salted skins are 
rubbed thoroughly on the flesh side with salt, folded into small 
bundles, and packed in barrels or casks. The dried skins are 
placed in bales, and a small quantity of naphthalene is put 
between each skin. This prevents moths and bugs from dam- 
aging the stock, and overcomes the tendency to heat. Skins 
from some countries are arsenic-cured, but this should be 
avoided as much as possible. 

Goatskins, as they come to the tanner, are designated by 
the name of the country or province from which they come, 



HIDES AND SKINS 23 

or from the point of shipment. They are graded according 
to weights and selections somewhat as indicated below : 

From China Average weight, pounds 

Light 1.25 

Medium 2.00 

Heavy 2.50 

Bulls over 3.00 

From India Weight, pounds 

Lights A's • 0.75 

Regular B's 1.00 

Large C's 1.50 

Heavy D's 2.00 

Bulls, BB's , over 2.00 

Northwestern and Amritsars from India < 

Lights 1.25 

Mediums 1.50 

Heavies 2.00 

Bulls over 2.00 

Regular South American 

Light A's 0.75 

Regular B's 1.15 

Medium C's 1.50 

Heavy D's 2.00 to 2.50 

Bulls, BB's over 2.50 

Brazilian 

Light A's 0.75 

Regular B's 1.00 

Medium C's 1.50 

Heavy D's 2.00 

Bulls, BB's over 2.00 

Figures 20 and 21 show goatskins as they arrive at a 
tannery. 

Spanish goatskins.. — These skins are noted for their fine 
grain, plumpness, and freedom from imperfection. They are 
cut open and folded down the back. The best are obtained 
from Valencia, Catalonia, Barcelona, and Seville; good skins 
also come from Leon and Castille, but those from the territory 
near the Portuguese boundary are inferior. Spanish skins 
come into market under the following selections : 

Class Weight, pounds 

No. 1 and 2 lights 1.25 

No. 1 and 2 regulars 2.25 

No. 1 and 2 heavies 2.50 

No. 1 and 2 extra heavies , 3.00 



24 



PRACTICAL TANNING 




Figure 20. — Warehouse in a goatskin tannery; stock being received 

and weighed. 




Figure 21. — Raw stock. Goatskins come from all parts of the world 
They arrive in a dry condition and before tanning are sorted 
into various grades and weights. 



HIDES AND SKINS 25 

In addition to these there are small kidskins used for glove 
leather. The light skins are sometimes known as 
"chevrettes." 

German goatskins. — Most of the skins produced in Ger- 
many are used by the domestic trade. In case of shipment, 
however, the best skins are retained, and a selection of A, B, 
and C's, corresponding to first, second, and third, are sorted 
for export, and are known as American selections. 

Italian goatskins. — Those from the northern part of Italy 
are of the best quality, and come from the districts of Rome 
and Tuscany. They are flat dried and selected for primes 
and seconds, which yield a good-weight leather. Skins from 
the southern provinces are of an inferior quality. They come 
from Naples, Puglia, Calabria, and the Island of Sicily. The 
Sicilian skins are known as Messinas and Palermos. These 
skins weigh from 2\ to 3 lb. each. 

Southern Europe goatskins. — Many skins originate in 
that part of Europe comprising Austria, Hungary, and the 
Balkan countries. Most of these skins are of good quality 
with fine grain, and are usually taken off the animal in such 
a manner that they remain "cased," that is, not cut open. 
They are flint dried, and their weight averages from 3| to 
3 1 pounds. 

Serbian skins are limited in number, but are of the highest 
grade. The Bosnian skins are somewhat inferior in character. 
Other skins come from Greece, Montenegro, Macedonia, and 
Albania. Skins coming from these provinces are usually 
shipped from the port of Trieste, while some of those from 
Macedonia and Greece come from Salonica. 

Turkish goatskins. — Under the general name of "Levant 
goatskins" are those originating in Asiatic Turkey. These 
skins are dry-salted, cut open, and folded flat. They are in- 
ferior to Balkan skins, being coarse in character and having 
considerable long black hair. The weight of the skins runs 
from 3^ to 3f lb. each. The stock coming from the Mediter- 
ranean side is of about the same quality as Asiatic skins. From 
the southern district of Bagdad comes a skin which, on ac- 



26 PRACTICAL TANNING 

count of defective grain, gives a low-grade leather. After 
being taken off, the skins are cased, dry-salted, and stretched 
lengthwise. Their weight runs from 3 to 3^ pounds. 

Russian goatskins. — Taken as a whole, Russia, including 
Siberia and central Asia, produces more goatskins than any 
other country in the world. The skins are packed at various 
points, and are brought to the animal fairs held at Tyumen 
and Nijni Novgorod, when they find their way to the mar- 
kets of Petropaulovsk, Orenburg, Kazan, and Semipalatinsk. 
Russian skins reaching America are known from the place of 
shipment, such as "Petropaul goat," "Turkestans." and 
"Bokharas." 

Petropaul skins are flint-dried and are mostly white-haired. 
The summer skins are short-haired and plump, whereas win- 
ter ones are long-haired and thin. They are classified as 
"werchural," primes and seconds, 25 lb. per dozen ; "mittel," 
primes, seconds, and winters, 20 lb. per dozen; and "lack" 
kids, 12 lb. per dozen. 

These skins contain considerable natural grease, and al- 
though they produce a high-grade leather, the tanner often 
encounters trouble from spew. 

Turkestan skins possess all the qualities of Petropaul skins, 
except that they are somewhat lighter. 

Bokhara goatskins are almost identical with Turkestans, 
except that they are short-haired and mostly black. Many 
Afghanistan and Persian skins also find their way to the 
American market, and, as their quality is inferior, they have 
detracted from the real value of Bokhara skins. Their weight 
is about the same as other Russian skins. 

North African goatskins. — The chief shipping ports for 
these skins are Algiers, Constantine, and Oran. The leather 
from all these skins is of fine grain and good quality. The hair 
is short and mostly white. They are cased and dry-salted, 
and are classified as heavies, weighing about 2 lb. each: mid- 
dles, If lb.; and lights, 1| pounds. 

Skins coming from Tunis and Sfax closely resemble those 



& 



HIDES AND SKINS 27 

coming from Algeria, although they are slightly inferior in 
grain and substance. 

Tripoli and Bengari produce a large quantity of skins, 
plump in character and fine of grain, which produce a very 
good leather. Both salted and flint-dried skins come from 
this district. 

High-grade skins are obtained from Morocco. Those from 
Tangiers and Fez are earthy salt-cured, cased, and of a brown- 
ish color. The hair is medium in length and of a reddish- 
brown color. Skins come into the American market also 
known as "Casablancas," "Mogadors," and "Marrakesh." 
The first mentioned are either red- or gray-cured, the red- 
cured skins being mostly cased. From Mogador and Marra- 
kesh the stock is identical in character and of good quality. 
These skins are cut open, and cured with a mixture of salt 
and camel manure, but on account of this treatment, they do 
not keep well. 

The Egyptian and Sudan skins are cased and salt-cured. 
The summer skins are short-haired and black, and, like other 
skins, are better during this season. The shipping points are 
Cairo and Alexandria. The selection includes : No. 1 heavies, 
2.3 lb. ; No. 1 mediums, 1.6 lb.; No. 1 lights, 1.25 lb. ; No. 1 
smalls, 1 lb. ; and No. 2, 1 lb. to | pound. 

South African skins. — The skins from this country are 
known to the trade as "Capes." Depending upon the point 
of shipment, they are classified as "Capetowns," "Algoabays," 
and "Kaffirs." Of these classes the first are considered to 
be of the highest grade owing to their plumpness, fine grain, 
and white hair. Their cure is a light brine, ■ and the skins 
are packed flat. The Algoabays are cured somewhat heavier 
than Capetowns; the hair is slightly longer and somewhat 
inferior in character. The Kaffir skins are inferior to the 
two grades first mentioned, being darker in appearance, hav- 
ing much longer hair, and being more heavily cured. 

Arabian goatskins. — The skins coming from the region of the 
Red Sea include those from northeastern Africa and Arabia. 
They are known to the trade as "Mochas," originate largely 



28 PRACTICAL TANNING 

in the Yemen province, and are shipped from Aden or Ho- 
deidah. Skins of a similar character also come by the way 
of Gataways. All of the skins are "cased and dry-salted. The 
hair is short and is mixed black and white. The selections 
include heavies, weighing from 2 to 2\ lb. each ; regulars, 
about \\ lb.; seconds, from 1 to 1 1/5 lb.; and long hairs, 
kids, and thirds. 

Many skins coming from this- region and packed in Abys- 
sinia, are known as "Herrar" skins; while skins are also ob- 
tained from Massowah, Somali,. Mogdeshur, Mombassa, and 
Zanzibar. 

Indian goatskins. — The most important country in the world 
for goatskins is India, which produces 30 per cent of the en- 
tire supply. Not only are thousands of skins exported in the 
raw condition, but many are bark-tanned by the natives and 
come into the market as "India-tanned." The best known 
and most highly prized Indian skins are the so-called "Patnas," 
which derive their name from the city of Patna in the Prov- 
ince of Bengal, from which they are shipped. East of Patna 
is a district furnishing the skins known as "Daccas." The 
Patna skins are dry-salted and tacked, whereas Daccas and 
Dinajpores are dry-salted and not tacked. 

The best Indian skins are produced in the district around 
the estuary of the Ganges, and are known as "Kushtias" and 
"Calcutta daissees." These skins are classified according to 
weight as follows : 

Class Pounds per 500 pieces Class Pounds per 500 pieces 

Extra heavies 850 to 950 Smalls 300 to 350 

Heavies 700 to 750 Kids 250 to 300 

Medium 500 to 575 Heavy seconds 750 to 850 

Light 400 to 475 Medium seconds 450 to 500 

Many skins are obtained from other provinces of India, 
among which may be mentioned "Oudhs," "Agras," "Pun- 
jabs," "Amritsars," and "Madras." 

Chinese goatskins. — These are of about the same nature, re- 
gardless of the port of shipment. They are classified as long 
hairs, medium hairs, and short hairs, the last being the best 



HIDES AND SKINS 29 

Quality The principal ports from which the skins are shipped 
are Tientsin, Chowching, Shantafoo, Pastingfoo, Hankow, 

Honan, and Shanghai. J _'. „ ., 

South American goatskins.— Argentina and Brazil are the 
chief countries in South America furnishing goatskins. Those 
from Brazil are more in demand and most highly prized by 
the tanner. These skins, named from the port of shipment, 
are known as "Buenos Aires," "Pernambucos," etc. 

A considerable number of skins also come from Mexico and 

the West Indies. 

Hogskins.-These, as a rule, are not taken off by the 
butcher, as the method of removing the bristles consists of 




w 



Figure 22.— Hogskin, showing charac- 
teristic grain. 

scalding and scraping the carcass. Figure 22 shows die char- 

acteristic grain. . , « . 

In some establishments, however, the skm is removed, but 
even then the take-off is very poor. Hogskins are des.rable 
for certain purposes, and there seems to be a growmg de- 
mand for leather made from this raw material Skins from 
loss the shoulders are the most desirable, and of course bnng 

^unTof vears, bacon strips have been worked into 



30 



PRACTICAL TANNING 



a marketable article, and find a growing demand in the trade. 
Sheepskins. — Of all the pelts of animals used in making 
leather that of the sheep exceeds all others. It is estimated 
by Alfred Seymour-Jones that there are more than 600,000,- 
000 sheep in the world, and of this number from 25 to 40 
per cent is slaughtered every year. As sheep are raised for 
their wool and flesh, and not for their skins, many of the lat- 




Figure 23. — Skinning out the legs of a sheep. 



ter are lost, but owing to the increased demand, this waste 
is gradually decreasing. The decline in the number of sheep 
— as well as cattle — being raised is a factor which is giving 
the tanner considerable cause for alarm. Figures 23, 24, 25, 
and 26 show some of the steps in flaying sheep. 

Although sheep form a separate group of animals, they 
pass by gradual stages into the goat classification. Thus the 
pelt may range from one with wool to one with coarse hair, 
while some sheep possess no hair nor wool. 



HIDES AND SKINS 



31 



The character of sheepskins depends upon the condition of 
the environment and method of feeding the stock. Soft- 
wooled skins possess a fine grain, while long-wooled skins 
have as a rule, a coarse, tough grain. Generally, the more 
woolly a skin is the more fat is found on the pelt; on the 




Figure 24.— Skinning over the flank of a sheep, 
other hand the less wool the skin carries the nearer the pelt 
approaches the character of the goat. _ 

Sheepskins are subject to numerous afflictions, all of which 
worry the tanner when he tries to convert the raw material 
into leather. The worst enemy to the sheep is the fly, or 
parasite, which acts as a means of transmitting disease from 
one animal to another. The diseases produced by parasites 
are sturdy or giddiness, louping ill and scab, while other 
damages are caused by fly-blow, and ticks. 



32 



PRACTICAL TANNING 



Of these various afflictions, that of scab is the most for- 
midable on account of its persistence and difficulty of eradi- 
cation. The presence of the disease is indicated by the falling 
of the hair from the part affected. If examined under the 
microscope, it will be noticed that the surface shows an erup- 
tion, and that numerous insects may be seen moving in and 




Figure 25. — Stripping-off over the back of a sheep. 



out among the hair roots. If the parasite is not killed, the 
disease will spread over the entire body. 

Sheep kids. — This pest is probably the most widely distrib- 
uted of the parasites attacking sheep. It belongs to the same 



HIDES AND SKINS 33 

order as the common house-fly, but is wingless. The kid does 
not lay eggs, but hatches them in the body of the parent in- 
sect. When the maggot is deposited, the development is so far 
advanced that it becomes a pupa under cover of the puparium. 
Each female produces above five pupae, at intervals of a few 
days, after which it dies. The mature insect sucks the blood 



Figure 26. — Fisting off a sheepskin. 

of the animal, causing great irritation at the point of attack. 
Sheep ticks. — The eggs of this insect are laid in large num- 
bers in swampy places ; the larvae, on hatching, attach them- 
selves to sheep, and, after feeding, fall to the ground and 
moult, after which they become nymphae. Again they attach 
themselves to the sheep, and after feeding fall off and moult 
a second time, then becoming adults. Once again as adults, 
they gorge themselves with blood, and the females fall to the 
ground for egg-laying. The ticks are found in sheep during 
the spring and summer months. The injury caused by the 



34 PRACTICAL TANNING 

blood-sucking is. that minute holes are made through the grain, 
thus causing a local inflammation, which destroys the grain 
and even the skin for some distance around the puncture. 

Lice. — These insects are very common on sheep, their pres- 
ence indicated by falling hair, itching, irritation, and unrest. 
The injury to the grain is somewhat similar to that caused 
by ticks. 

Fly-blow. — This is caused by sheep maggot-fly. The fly 
deposits the eggs upon the- backs of the longer- wooled 





.& 



.if *v 




^6 



Figure 27. — Sheepskin, showing char- 
acteristic grain. 

sheep, as deep in the wool as it can reach. The act of deposit- 
ing the eggs is termed "striking," by the sheepman. The 
eggs hatch quickly, and the larvae burrow into the skin, caus- 
ing excruciating pain, which, unless treated, may often cause 
the death of the animal, a death due to the sheep being eaten 
by the maggot while alive. 

Sheepskins come to the tanner either in the hair or in a 
pickled condition. The latter skins have been pulled by the 
fellmonger for the wool. The largest number of skins come 
from New Zealand and the British Isles, while, at the same 
time, a considerable number of domestic skins are available 
Figure 27 shows characteristic grain. 



HIDES AND SKINS 



35 



Other hides and skins. — Although the hides and skins 
enumerated constitute the bulk of the raw material from which 
leather is produced, it must not be concluded that they are 
the only source, as the covering of many other animals — even 
the skin of fish — enters into the production of this commodity. 

Without going into detail, it may be well to mention that a 
large amount of leather is produced from the covering of the 
deer, kangaroo, buffalo, dog, seal, walrus, shark, porpoise, 
whale, sturgeon, alligator, crocodile, lizard, and many others; 




Figure 28. — Lambskin. 




Figure 29.— Kid skin. 



Figure 30. — Kangaroo skin. 



36 



PRACTICAL TANNING 



while furs are produced from a large variety of animals. 
Figures 28, 29, 30, 31, 32, and 33, represent the characteristic 
srrain of the various kinds of skins indicated. 

Disinfection of hides. — The number of hides and skins 
imported into the United States annually amounts to many 
millions, (700,000,000 lb., exclusive of furs, in 1920, calcu- 
lated on a "green" basis, when 1 lb. of dry hide equals 2 lb. 
of green hide). Since these hides and skins come from all 
parts of the globe, there is great danger of their bringing in 




Figure 31. — Human skin. 




Figure 32. — Sealskin. 



Figure 33. — Alligator skin. 



HIDES AND SKINS 37 

infectious diseases, among the most dangerous of which is 
anthrax. As the anthrax spore has great resisting power, 
many methods of disinfection have been suggested. Among 
the numerous processes which have been suggested, that pro- 
posed by Seymour-Jones has attracted much attention. Other 
methods have been investigated, among them being the treat- 
ment devised by Schattenfroh. 

Seymour-Jones purposes to use mercuric chloride and form- 
ic acid. By this method it is claimed that the formic acid 
causes the hide substance to swell, thus furnishing a favor- 
able condition for the action of this salt. The dilutions rec- 
ommended are 1 part mercuric chloride in 5,000 parts of 
water, and 1 per cent of formic acid, and time of treatment 
24 hours. After disinfection, the hides are placed in a 10° 
Be. salt solution when they will fall, and thus be brought to 
the condition of green-salted stock. 

The Schattenfroh method consists in immersing the hide 
for 48 hours in a 10° Be. salt solution containing 2 per cent 
of hydrochloric acid. This method is being carried out in 
many tanneries, and by replenishing the hydrochloric acid re- 
moved by the hide, is much less expensive than the Seymour- 
Jones process. 

The above methods for disinfection in the case of anthrax 
apply equally well for other infections, such as rinderpest and 
foot-and-mouth disease. 

Regulation of the U. S. Government.— The Government 
regulations covering disinfection are set forth in the following 
orders : 

TTNTTED STATES TREASURY DEPARTMENT AND DEPART- 
MENT OF AGRICULTURE 

Pomll!lf ; nn , Governing the Sanitary Handling and Control of Hides, 

Regulations ^°*f ™L n p aring s, and Glue Stock, Sheepskins and 

r^cE Sd ? Parts thereof? Ha r, Wool, and Other Animal By- 

Pr^ducts? Say Straw forage, or Similar Material Offered for En- 

try into the United States. 

Effective January 1, 1918. 

Washington, D. C, October 15, 1917. 
Under authority of the act of Congress approved October 3, 1913, en- 
titled "An art to reduce tariff duties and to provide revenue for the 



38 PRACTICAL TANNING 

Government, and for other purposes" (38 Stat., 114), and the act of 
Congress approved February 2, 1903, entitled "An act to enable the 
Secretary of Agriculture to more effectually suppress and prevent the 
spread of contagious and infectious diseases of live stock, and for other 
purposes" (32 Stat, 791), the following regulations are issued for the 
purpose of preventing the introduction of anthrax, foot-and-mouth disease, 
and rinderpest from a foreign country into the United States. 

Regulation I 

HIDES AND SKINS ( 

Section 1. All hides of meat cattle, calfskins, buffalo hides, sheepskins, 
goatskins, and deerskins offered for entry into the United States (except 
abattoir and hard, sundried hides and skins as hereinafter provided for) 
may be imported from any country maintaining an efficient veterinary 
inspection system when accompanied by a certificate signed by an official 
veterinary inspector of such country, or, in the absence of such official 
veterinary inspector, by a United States consular officer, stating that 
anthrax is not prevalent and that neither foot-and-mouth disease nor 
rinderpest exists in the locality in which the hides or skins originated. 
Those articles may also be imported from any country which does not 
maintain an official veterinary inspection system when accompanied by a 
United States consular certificate stating that anthrax is not prevalent, and 
that neither foot-and-mouth disease nor rinderpest exists in the locality 
in which the hides or skins originated. In lieu of a certificate showing 
the non-prevalence of anthrax and the non-existence of foot-and-mouth 
disease and rinderpest, a certificate signed by one of the aforementioned 
officials stating that the hides or skins have been disinfected under his 
supervision by any of the methods approved or which may hereafter be 
approved by the Chief of the Bureau of Animal Industry, will be accepted. 

Sec. 2. All hides or skins offered for entry into the United States 
(except abattoir and hard, sundried hides and skins as hereinafter pro- 
vided for) which are not accompanied by any of the certificates prescribed 
.in section 1 of this regulation, or which are accompanied by certificates 
which do not comply with the requirements or purposes of these regula- 
tions, may be imported from any country upon the conditions that they 
will be consigned from port of entry to an establishment having proper 
facilities for their sanitary control and disinfection; that they will move 
from port of entry to the establishment in cars or approved containers, 
sealed either with customs seals or seals of the Department of Agriculture; 
that they will be handled at port of entry and en route to such establish- 
ment in accordance with the provisions of these regulations, and that 
they will be disinfected by one of the methods approved, or which may 
hereafter be approved, by the Chief of the Bureau of Animal Industry. 
Seals of the Department of Agriculture shall be affixed to said cars and 
containers only by inspectors of the Bureau of Animal Industry, or by 
customs officers, and may be broken only by inspectors of the Bureau 
of Animal Industry, by customs officers, or by other persons authorized 
so to do by the Bureau of Animal Industry. Customs seals shall in no 
case be broken except by customs officers. 

Regulation II 

HARD, SUNDRIED HIDES AND SKINS, AND ABATTOIR HIDES AND SKINS 

Section 1. Hard, sundried hides and skins may be imported without 
disinfection if certified as required in section 1 of Regulation I to be 
from a locality where anthrax is not prevalent, if the bale? or hides are 



HIDES AND SKINS 39 

distinctly marked for identification, each shipment showing invoice num- 
ber, names and addresses of consignee and consignor, as such hard, sun- 
dried hides and skins so certified showing freedom from anthrax can be 
considered as having been disinfected by the process of curing and need 
not be submitted to any further treatment. Hard, sundried hides or skins 
may be imported without being certified to be from a locality where 
anthrax is not prevalent, upon the conditions prescribed in section 2, 
Regulation I, for the importation of uncertified hides and skins. 

Sec. 2. Abattoir hides and skins taken from animals slaughtered in 
Sweden, Norway, Denmark, Australia, New Zealand, Great Britain, 
Uruguay, Argentina, Brazil, and Venezuela when accompanied by a 
certificate of an official veterinarian of the country where such animals 
were slaughtered showing that such hides or skins were taken from 
animals free from disease at the time of slaughter, may be imported 
into the United States without disinfection. Abattoir hides and skins 
from the countries specified, which are uncertified, and abattoir hides and 
skins from countries other than those specified, may be imported subject 
to the requirements of Regulation I, 

Regulation III 

GLUE STOCK 

Fleshings, hide cuttings, and parings, or glue stock may be imported 
without disinfection — 

(a) If accompanied by a certificate signed by one of the officials 
mentioned in section 1 of Regulation I, showing the non-prevalence of 
anthrax in the locality of origin ; or 

(&) If shown upon entry to have been disinfected by heat; or 

(c) If shown to have been disinfected by acidulation; or 

(d) If shown to have been disinfected by soaking in a milk of lime 
or a lime paste; or 

(e) If shown to have been dried by exposure to the action of the sun 
and air for a sufficient time to render each piece of the hardness of a 
sundried hide. 

If the said materials are not accompanied by the certificate described in 
paragraph (a), and are not shown to have been treated by one of the 
methods above indicated, they may be imported, upon the condition that 
the consignee or his agent files a satisfactory bond or agreement that said 
materials and their containers will be handled or disinfected in a manner 
acceptable to the Bureau of Animal Industry before distribution from the 
factory or establishment to which consigned. 

Regulation IV 

BONES, HOOFS, AND HORNS 

Section 1. Bones, hoofs, and horns which are clean, dry, and free 
from pieces of hide, flesh, or sinews may be imported without disinfection. 

Sec. 2. Bones, hoofs, and horns, with pieces of hides or tendons at- 
tached, and also horn piths, may be imported upon the conditions that 
said materials be forwarded to a factory or other establishment in cars 
or approved containers sealed in the manner prescribed in section 2, 
Regulation I, and that the consignee or his agent files a satisfactory bond 
or agreement that such materials and their containers will be handled or 
disinfected in a manner acceptable to the Chief of the Bureau of Animal 
Industry. 



40 PRACTICAL TANNING 

Regulation V 

WOOL AND HAIR 

Section 1. Raw wool or hair clipped from healthy live animals, scoured 
wool and hair, and noils of wool and hair which have been properly 
scoured may be imported without disinfection or certification. 

Sec. 2. Picked or pulled wool or hair, when accompanied by an affidavit 
of the exporter designating the bales or packages thereof by their 
markings, indicating the consignor, consignee, and number of the invoice, 
and stating that all the wool or hair contained in the bales or packages 
came from animals free from anthrax, may be imported upon the condi- 
tions that the consignee or owner of the wool or hair, or his agent, files 
a satisfactory bond or agreement assuring proper facilities of disinfection 
at the establishment to which the shipment is consigned and that such 
wool or hair will be disinfected by proper exposure to a temperature of 
not less than 165° F. prior to any transfer or reshipment from such estab- 
lishment. If such wool or hair is unaccompanied by the above-mentioned 
affidavit it may be imported upon condition that the consignee or owner 
thereof or his agent files a satisfactory bond or agreement assuring 
proper facilities for disinfection at the establishment to which the ship 1 
ment is consigned and that all of such wool or hair will be disinfected by 
proper exposure to a temperature of not less than 200° F. for at least 15 
minutes prior to any transfer or re-shipment from such establishment. 

Sec. 3. Importation of abattoir pulled wool will be permitted without 
restrictions from any country maintaining an efficient veterinary inspection 
system, when accompanied by a certificate signed by an official veterinary 
inspector of such country, of, in the absence of such official veterinary 
inspector, by a certificate of a United States consular officer of the locality 
from which shipped to the effect that said wool was procured from sheep 
slaughtered therein and passed under Government inspection, and that 
in the process of wet pulling and drying it has been subjected to a 
temperature of not less than 165° F. Such certificate shall indicate the 
number of bales, marks, names, and addresses of consignor and consignee, 
locality of origin, date of shipment, invoice number, and transporting 
vessel, and shall also show that the consignment consists of abattoir pulled 
wool which, in the process of wet pulling and drying, has been subjected 
to a temperature of 165° F. 

Sec. 4. Wool or hair not otherwise provided for in these regulations, 
or not complying with the provisions thereof, may be imported upon the 
conditions that such articles be shipped from port of entry to destination 
in cars or satisfactory containers, sealed in the manner prescribed in 
section 2 of Regulation I ; that the destination be a factory or establish- 
ment having satisfactory facilities for disinfecting the same, and that they 
will there be disinfected by proper exposure to a temperature of not 
less than 200° F. for at least 15 minutes, or in such mannef as may be 
directed by the Chief of the Bureau of Animal Industry, prior to any 
transfer or reshipment therefrom. Such wool or hair may be stored in 
bond at the port of entry, subject to shipment and disinfection, as herein 
provided, on being released from bond. The consignee, owner, or his agent 
will be required to file a satisfactory bond or agreement to fulfill all 
requirements as to shipment and disinfection. 

Regulation VI 

certificates from other than official veterinarians and consular 

officers 

Section 1. Whenever it shall be determined by the Secretary of Agri- 
culture, after investigation, that in any foreign country or locality thereof 



HIDES AND SKINS 41 

in which no official veterinarian of the Government or United States 
consular officer is located, there is a satisfactory qualified official, authorized 
by the Government of such foreign country to sign and issue certificates 
stating that anthrax is not prevalent and that neither foot-and-mouth 
disease nor rinderpest exists in the locality from which articles enumerated 
in these regulations are shipped, to sign and issue other certificates, to 
make affidavits and other declarations, and to supervise the shipment of 
hides and skins, glue stock, and other animal by-products, as specified in 
the regulations, due notice will be given of such determination, and 
thereafter such official may sign and issue the said certificates, make the 
said affidavits and declarations, and supervise the shipment of hides and 
skins, glue stock, and other animal by-products, in manner and form 
prescribed in the regulations; and such acts performed by the said 
official shall have the same force and effect as if performed by an official 
veterinarian of the country of origin or by an United States consular 
officer. 

Sec. 2. The name of each foreign official authorized to do and perform 
the acts specified in section 1 of this regulation, when submitted to and 
approved by the Secretary of Agriculture, will be_ published, and the 
Chief of the Bureau of Animal Industry shall file with each such official 
a copy of these regulations and copies of amendments which may hereafter 
be made thereto. No act specified in section 1, performed by a foreign 
official, shall be recognized unless performed by an official whose name 
has been published, as required herein, and whose authority to do such 
acts has not been revoked. 



Regulation VII 

HAY, STRAW, ETC., AND MEATS PACKED IN HAY OR STRAW 

Section 1. On account of the existence of foot-and-mouth disease in 
the countries of continental Europe and South America, and the imprac- 
ticability of disinfecting hay and straw used as the packing on meats 
offered for entry without injuring the meats for food purposes, the entry 
into the United States from any of those countries of any meats -packed 
in hay or straw is prohibited. 

Sec. 2. Bran, middlings, and mill feed may be imported from Argen- 
tina without being disinfected as prescribed in section 4 of this regulation 
if accompanied by- an affidavit of the shipper, showing that such bran, 
middlings, or mill feed was conveyed by chutes directly from the mill 
in which produced into the vessels transporting the same to the United 
States. 

Sec. 3. Because of lack of danger of the communication of disease 
through the importation of hay, straw, forage, and similar materials, 
including bran, middlings, or other mill feed originating in and trans- 
ported directly from Great Britain, Ireland, the Channel Islands, Canada, 
and Mexico, such articles may be imported into the United States from 
these countries as long as the above condition continues to exist without 
being disinfected as prescribed in section 4 of this regulation. 

Sec. 4. Except as otherwise provided in this regulation, all hay, straw, 
forage, or similar materials, including bran, middlings, or other mill 
feed, offered for importation from any foreign country, shall be disin- 
fected in a manner prescribed by the Chief of the Bureau of Animal 
Industry, at the expense of the owner, before being unloaded from the 
vessel or conveyance bringing the same into any port of the United States, 
and when unloaded and landed shall be stored and held in quarantine for 
a period of not less than three months at some place acceptable to the 
Chief of the Bureau of Animal Industry, and under directions prescribed 
by him. 



42 PRACTICAL TANNING 

Regulation VIII 

CANADA 

Because of the lack of danger of the introduction of disease into the 
United States through the importation of the articles enumerated in 
these regulations originating in and transported directly from Canada, 
such articles may be imported from Canada as long as the above condition 
continues to exist without being disinfected or certified as prescribed by 
these regulations. 

Regulation IX 

PRODUCTS FROM DISEASED ANIMALS 

Importation into the United States of any animal by-products, taken 
or removed from animals affected with anthrax, foot-and-mouth disease, 
or rinderpest, is prohibited. 

Regulation X 

METHODS FOR DISINFECTION OF HIDES, SKINS, AND OTHER MATERIALS 

Hides, skins, and other materials, required by these regulations to be 
disinfected shall be subjected to disinfection by methods found satisfactory 
and approved from time to time by the Chief of the Bureau of Animal 
Industry of the United States Department of Agriculture. The Chief 
of the Bureau of Animal Industry is authorized to revoke from time 
to time any methods which have been approved by him. 

Regulation XI 

DISINFECTION OF CARS, BOATS, OTHER VEHICLES, AND PREMISES 

Section 1. Cars, boats, other vehicles, yards, and premises which have 
been used in the transportation, handling, and storing of uncertified or 
non-disinfected imported hides, skins, and parts thereof, hair, wool, and 
other animal by-products, hay, straw, forage or similar material, permitted 
entry subject to disinfection, shall be cleaned and disinfected under the 
supervision of the Bureau of Animal Industry, as indicated in Regulation 
XII, and in the manner provided in sections 2 and 3 of this regulation. 
Except as hereinafter provided in these regulations, cars, boats, and other 
vehicles which have been used in the transportation of uncertified or 
non-disinfected imported hides, skins, and parts thereof, hair, wool, and 
other animal by-products, hay, straw, forage, or similar material, per- 
mitted entry subject to disinfection, shall not be moved in interstate or 
foreign commerce until the said cars, boats, and other vehicles have been 
cleaned and disinfected under supervision of the Bureau of Animal In- 
dustry in accordance with sections 2 and 4 of this regulation. 

Sec. 2. Paragraph 1. Cars required by these regulations to be cleaned 
and disinfected shall be treated in the following manner: Collect all 
litter and other refuse therefrom and destroy by burning or other ap- 
proved methods, clean the exterior and interior of the cars, and saturate 
the entire interior surface, including the inner surface of the car doors, 
with a permitted disinfectant. 

Paragraph 2. Boats required by these regulations to be cleaned and 
disinfected shall be treated in the following manner: Collect all litter 
and other refuse from the decks, compartments, and all other parts of the 
boat used for the transportation of materials covered by these regula- 
tions, and from the portable chutes or other appliances or fixtures used 



HIDES AND SKINS 43 

in loading and unloading same, and destroy the litter and other refuse 
by burning or by other approved methods, and saturate the entire surface 
of the said decks, compartments, and other parts of the boat with a per- 
mitted disinfectant. 

_ Paragraph 3. Buildings, sheds, and premises required by these regula- 
tions to be disinfected shall be treated in the following manner : Collect 
all litter and other refuse therefrom and destroy the same by burning 
or other approved methods and saturate the entire surface of the fencing, 
chutes, floors, walls, and other parts with a permitted disinfectant. 

Sec 3. Paragraph 1. All hides, skins, and other materials ■ subject 
to disinfection at destination under the provisions of these regulations shall 
be entered at ports having docking and unloading facilities separate and 
apart by not less than 100 feet, from yards, premises, roads, or runways 
where cattle and other ruminants and swine are kept, held, conveyed, or 
driven except for immediate slaughter. No animals of the species named, 
except for immediate slaughter, shall be permitted on any dock or prem- 
ises where imported hides or other materials subject to disinfection 
at destination are being unloaded, stored, or handled within 24 hours 
following the completion of such handling, unless the said hides or other 
materials have been removed and the place or places where they were 
unloaded, stored, or handled, or with which they were in contact, have 
been cleaned and disinfected in a manner approved by the Chief of the 
Bureau of Animal Industry. 

Paragraph 2. Except as otherwise provided in these regulations, all 
such hides, skins, and other materials subject to disinfection shall be 
loaded and shipped under official supervision and under seals as prescribed 
in section 2 of Regulation I. 

Paragraph 3. Dust and refuse at docks, unloading places, and all ware- 
houses and other establishments shall be controlled. All dust and other 
refuse shall be collected and destroyed by burning or other approved 
methods. 

Sec. 4. Paragraph 1. The substances permitted for use in disinfecting 
cars, boats, other vehicles, and premises are as follows : 

(a) Compound solution of cresol, U. S. P., at a dilution of at least 
4 fluid ounces to 1 gallon of water. 

(b) A permitted "saponified cresol solution" at a dilution of at least 
4 fluid ounces to 1 gallon of water. 

(c) Liquified phenol (liquified carbolic acid) at a dilution of at least 
6 fluid ounces to 1 gallon of water. 

(d) Chlorid of lime (U. S. P. strength, 30 per cent available chlorin) 
at a dilution of 1 pound to 3 gallons of water. 

Paragraph 2. The use of "saponified cresol solution" as a substitute for 
compound solution of cresol, U. S. P., as a disinfectant is permitted, pro- 
vided that such "saponified cresol solution" shall conform to the following 
requirements : 

(a) The formula of the product shall employ not less than 28 per cent 
by weight of linseed oil. Either caustic potash, caustic soda, or a mixture 
of caustic potash and caustic soda may be used to saponify the linseed 
oil. The cresol used shall be at least 95 per cent pure, and enough of 
this commercial grade of cresol (cresylic acid) shall be employed in com- 
pounding the disinfectant to bring the actual amount of cresol in the 
finished product up to 50 per cent. 

(b) The product shall remain a homogeneous liquid when cooled to 
32° F. It shall contain substantially no unsaoonified linseed oil or excess 
alkali. Tt shall be readily soluble in cold distilled water; the solution shall 
be practically clear and shall contain no globules of undissolved oil or 
cresylic acid. 

(c) Manufacturers wishing to offer saponified cresol solution as indi- 
cated above for use in official disinfection shall first submit a sample of at 
least 8 ounces for examination, together with a statement of the formula 



44 PRACTICAL TANNING 

employed and a guaranty that the product will be maintained of a quality 
uniform with the sample submitted. 

(d) To prevent confusion, each product shall bear a distinctive trade 
name or brand, together with the name of the manufacturer or distributor. 
There shall be no mention of the United States Department of Agriculture 
or the Bureau of Animal Industry on the labels, containers, or printed 
matter accompanying products permitted to be used in official disinfection. 
The permitted saponified cresol solution shall be used at a dilution of 
at least 4 ounces of the solution to 1 gallon of water. 

Regulation XII 

■ PLACARDING CARS AND MARKING BILLING 

.Section 1. Transportation companies shall securely affix to and main- 
tain upon both sides of all cars carrying uncertified or non-disinfected 
imported hides, skins, and parts thereof, hair, wool, and other animal by- 
products, permitted entry subject to disinfection, durable placards not 
less than 5s by 8 inches in size, on which shall be printed with permanent 
black ink and in bold-faced letters not less than H inches in height the 
words "UNCERTIFIED IMPORT ANIMAL PRODUCT." These 
placards • shall also bear the words "CLEAN AND DISINFECT THIS 
CAR." Each of the waybills, conductors' manifests, memoranda, and 
bills of lading pertaining to such shipments shall have the words "UN- 
CERTIFIED IMPORT ANIMAL PRODUCT, CLEAN AND DISIN- 
FECT CAR," plainly written or stamped upon its face. If for any 
reason the placards required by this regulation have not been affixed to the 
car, or the billing has not been marked by the initial or the connecting 
carrier, or the placards have been removed, destroyed, of rendered illegi- 
ble, the placards shall be immediately affixed or replaced, and the billing 
marked by the initial of connecting carrier, the intention being that the 
billing accompanying the shipment shall be marked and the car placarded 
as herein specified from the time such shipments leave the port of entry 
until they are unloaded at final destination and the cars are cleaned and 
disinfected as required by Regulation XI. 

Sec. 2. If it is necessary to unload enroute any of the products specified 
in this regulation, the car from which the transfer is made and any part 
of the premises at the point of transfer which may have been contaminated 
shall be cleaned and disinfected by the transportation company, in accord- 
ance with the provisions of Regulation XI, and the transportation com- 
pany shall immediately report the transaction by telegraph, to the Chief 
of the Bureau of Animal Industry, Washington, D. C. Such report 
shall include the information indicated as follows: (a) Nature of 
emergency; (b) place where product was unloaded; (c) original points 
of shipment and destination; (d) number and initials of the original car; 
also number and initials of the car into which the product is reloaded in 
case original car is not used. 

Sec. 3. Cars required by these regulations to be cleaned and disin- 
fected shall be treated in the manner specified in Regulation XI, under the 
supervision of the Bureau of Animal Industry, by the final carrier at 
destination as soon as possible after unloading and before the same are 
moved from such final destination for any purpose except as otherwise 
hereinafter provided. 

When the products are destined to points at which an inspector of the 
Bureau of Animal Industry and proper facilities are maintained, the cars 
shall be cleaned and disinfected at such points under supervision of such 
inspector. 

When the products are destined to points at which an inspector or 
other duly authorized representative of the Bureau of Animal Industry 
is not maintained, the transportation company shall seal, bill, and forward 



HIDES AND SKINS 45 

the infectious cars to a point to be agreed upon between the transportation 
company and the Bureau of Animal Industry, and at which an inspector 
is maintained. The transportation company shall there clean and disinfect 
the said cars under the supervision of the Bureau of Animal Industry. 
When the products are destined to points at which an inspector of the 
Bureau of Animal Industry is maintained, but at which proper facilities 
can not be provided, the transportation company may, upon permission 
first secured from the Bureau of Animal Industry, seal, bill, and forward 
the cars to a point at which an inspector of the Bureau of Animal In- 
dustry is maintained and proper facilities provided, and there clean 
and disinfect the said cars under the supervision of the Bureau of 
Animal Industry. 

Regulation XIII 

TERRITORIAL POSSESSIONS 

These regulations shall be applicable to all hides, fleshings, hide cuttings, 
parings, and glue stock, sheepskins and goatskins and parts thereof, hair, 
wool, and other animal by-products, hay, straw, forage, or similar material 
which is offered for entry into the United States from any place under 
the jurisdiction of the United States to which the animal quarantine laws 
of this country do not apply. 

Prior Order Annulled 

Treasury Department and Department of Agriculture Joint Order No. 
1, of October 21, 1916, and all amendments thereto, shall cease to be 
effective on and after January 1, 1918, on and after which date this order, 
which for purposes of identification is designated as United States 
Treasury Department and Department of Agriculture Joint Order No. 2, 
shall become and be effective until otherwise ordered. 

L. S. Rowe, 
Acting Secretary of the Treasury. 
D. F. Houston, 

Secretary of Agriculture. 

UNITED STATES DEPARTMENT OF AGRICULTURE 

BUREAU OF ANIMAL INDUSTRY 

Special Order Prescribing Methods for the Disinfection of Hides, 
Skins, Fleshings, Hide Cuttings, Parings, and Glue Stock, and Other 
Animal By-Products, Hay, Straw, Forage, or Similar Material Of- 
fered for Entry into the United States, and the Containers of Glue 
Stock, Bones, Hoofs, and Horns so Offered for Entry. 

United States Department of Agriculture, 
Bureau of Animal Industry 

District of Columbia, December 14, 1917. 
In accordance with the provisions of the United States Treasury De- 
partment and Department of Agriculture Joint Order No. 2, of October 
15, 1917, "Regulations governing the sanitary handling and control of 
hides, fleshings, hide cuttings, parings, and glue stock, sheepskins and goat- 
skins and parts thereof,, hair, wool, and other animal by-products, hay, 
straw, ; forage, or similar material offered for entry into the United 
States," the following methods for the disinfection of the above-named 
materials and articles are hereby prescribed, effective January 1, 1918. 



46 PRACTICAL TANNING 

I. DISINFECTION OF HIDES AND SKINS PRIOR TO SHIPMENT 

Hides and skins disinfected prior to shipment as provided by regulation 

I, section 1, of said Joint Order No. 2, must be disinfected by one of 
the following methods : 

(a) By immersion for not less than 24 hours in a 1 to 1,000 bichlorid 
of mercury solution. 

(b) By immersion for not less than 20 hours in a solution containing 
2 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent 
sodium chlorid. 

(c) By immersion for not less than 40 hours in a solution containing 
1 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent 
sodium chlorid. 

(J) By immersion for not less than 24 hours in a solution containing 

1 per cent formic acid, and mercuric chlorid in the proportion of 1 part 
to 2,500 parts of the solution. Hides or skins treated by this process shall 
be held for two weeks following the treatment before neutralization. 

(e) By de-hairing and pickling in a solution of salt containing a definite 
percentage of mineral acid and packing in barrels or casks while still wet 
with such solution, provided the hides or skins are not neutralized within 
30 days after being so packed. 

II. DISINFECTION OF HIDES AND SKINS AFTER ARRIVAL IN THE UNITED STATES 

Hides and skins required by Regulation 1, section 2, and Regulation 2 of 
said Joint Order No. 2 to be disinfected on arrival at a United States port 
of entry shall be moved to an approved warehouse at such port or in sealed 
cars or containers to an establishment having proper facilities for their 
sanitary control and disinfection. They shall be stored and handled prior 
to disinfection in compartments set aside for that purpose, and all hides 
and skins stored or handled in such compartments shall be treated in 
accordance with the following rules : 

1. All dust, litter, or waste arising from sorting, cutting handling, or 
moving said hides or skins prior to soaking shall be burned or disinfected 
by exposure to a temperature of not less than 100° C. (212° F.) moist 
heat for not less than 15 minutes. 

2. The hides and skins shall be subjected to disinfection by one of the 
following methods : 

(a) By immersion for not less than 20 hours in a solution containing 

2 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent 
sodium chlorid. 

(6) By immersion for not less than 40 hours in a solution containing 
1 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent 
sodium chlorid. „ 

(c) By immersion for not less than 24 hours in a solution containing 
1 per cent formic acid, and mercuric chlorid in the proportion of 1 part 
to 2,500 parts of the solution. Hides or skins treated by this process shall 
be held for two weeks following the treatment before neutralization. 

(d) By immersion for not less than 48 hours in a 1 to -1,000 bichlorid of 
mercury solution. 

(e) By immersion for not less than 6 days in a 1 to 5,000 bichlorid of 
mercury solution, plus not less than 5 days in lime of the usual strength 
for de-hairing. 

Or, in lieu of disinfection by one of the foregoing mentioned processes, 
the effluent shall be subjected to treatment by one of the following 
methods : 

(/) Heat the effluent from soak vats, mill drums, breaking machines, or 
other similar equipment to a temperature of 100° C. (212° F.) and main- 
tain at that temperature for at least one minute. 

(g) Treat the effluent from soak vats, mill drums, breaking machines, 
and other similar equipment with chlorin in such manner and in such 



HIDES AND SKINS 47 

amount (not less than 250 parts per million) as to secure efficient 
disinfection. 

(h) Subject the effluent from soak vats, mill drums, breaking machines, 
and other similar equipment to filtration, the effluent from the filters to be 
treated with chlorin in sufficient amount and in such manner as to secure 
efficient disinfection : Provided, however, That in this method of treatment 
the sludge which collects on the filters shall be subjected to disinfection by 
heating at a temperature of not less than 100° C. (212° F.) for not less 
than 15 minutes. 

(i) Treat the effluent from soak vats, mill drums, breaking machines, 
and other similar equipment with 50 parts of chlorin per million parts of 
effluent and heat at not less than 80° C. (176° F.) for not less than 30 
minutes. . 

(/) In the case of sheepskins and goatskins, until further notice, by 
immersion for not less than 12 hours in a solution of milk of lime con- 
taining the equivalent of 5 per cent of calcium oxid (CaO). 

III. DISINFECTION OF GLUE STOCK 

All fleshings, hide cuttings, and parings or glue stock shall be moved 
from the port of entry to an establishment having proper facilities for 
the sanitary control and disinfection of such materials, in cars or approved 
containers sealed with either Department of Agriculture or customs seals, 
and upon arrival at the establishment, disinfected before removal there- 
from by one of the following methods : 

1. By heating in water at a temperature of 100° C. (212° F.) for not 
less than 15 minutes, or by heating in water at a temperature of* not less 
than 82° C. (180° F.) for not less than four hours. 

2. By soaking in milk of lime or lime paste for not less than 24 hours. 

3. By soaking in water containing not less than 2 per cent of absolute 
hydrochloric acid for not less than 20 hours. 

4. By soaking in water containing not less than 1 per cent of absolute 
hydrochloric acid for not less than 40 hours. 

IV. DISINFECTION OF BONES 

1. All horn pith and porous bones classed as glue stock must be moved 
from the port of entry to an establishment having proper facilities for 
their sanitary control and disinfection, in cars or approved containers 
sealed with either Department of Agriculture or customs seals, and, upon 
arrival at the establishment, disinfected before removal therefrom as 
provided for glue stock. 

2. Bones with pieces of hide or tendons attached and all other bones 
not otherwise provided for shall be moved from the port of entry to an 
establishment having proper" facilities for their sanitary control and disin- 
fection, in cars or approved containers sealed with either Department of 
Agriculture or customs seals, and upon arrival at the_ establishment, 
disinfected before removal therefrom by one of the following methods: 

(a) By heating in water at a temperature of 100° C. (212° F.) for not 
less than 15 minutes. o 

(b) By heating in water at a temperature of not less than 82 C. 
(180° F.) for not less than four hours. 

V. DISINFECTION OF HOOFS AND HORNS 

Hoofs and horns shall be moved from the port of entry to an establish- 
ment having proper facilities for the sanitary control and disinfection of 
such materials, in cars or approved containers sealed with either Depart- 
ment of Agriculture or customs seals, and disinfected before removal 
from the establishment by heating in water at a temperature of not less 
than 74° C (165° F.) for not less than 15 minutes. Bones removed from 



48 PRACTICAL TANNING 

horns and hoofs that are required to be disinfected shall be handled as 
provided for glue stock. 

VI. DISINFECTION OF CONTAINERS OF GLUE STOCK, BONES, HOOFS, AND HORNS 

Containers of glue stock, bones, hoofs and horns, which under the pro- 
visions of Regulations III and IV of Joint Order No. 2, are required to be 
disinfected, shall be handled as follows: 

(a) The containers shall be burned; or 

(b) The containers shall be subjected to moist heat at a temperature not 
less than 100° C. (212° F.) for not less than IS minutes. 

VII. DISINFECTION OF HAY, STRAW, ETC. 

Hay, straw or similar materials shall be placed in a compartment made 
tight by sealing all crevices therein and then subjected to treatment with 
formaldehyde gas applied as follows: 

The formaldehyde gas shall be generated from solutions of formalde- 
hyde containing not less than 37 per cent actual formaldehyde by pouring 
the formaldehyde solution onto pulverized potassium permanganate, the 
formaldehyde solution and the potassium permanganate being employed in 
the proportion of 20 ounces of formaldehyde solution by weight and 16% 
ounces of potassium permanganate by weight to each 1,000 cubic feet of 
space in the compartment to be disinfected. Bales of hay, straw, or other 
material shall be piled in block so that not more than 6 inches of any sur- 
face of the bale is in contact with another bale, or if deemed necessary 
by the inspector, the bales shall be broken and the straw or hay loosened, 
so that a satisfactory penetration of the formaldehyde gas may be obtained. 
The disinfection with formaldehyde gas shall be carried out in compart- 
ments in which the temperature is not less than 65° F. 

J. R. Mohler, 

Chief of Bureau of Animal Industry. 

Hide structure. — Although the skins of the various ani- 
mals seem at first glance to have little in common, they pre- 
sent, on closer examination, much similarity of structure. The 
difference in texture and thickness, on the other hand, makes 
their practical application vary greatly. The skins of lizards, 
alligators, fish, and serpents differ from those of higher ani- 
mals in that the epidermis becomes harder and forms scales. 
Figures 34 and 35 show cross-sections of hide. 

The skin is not merely a covering for the animal, it is at 
the same time the seat of the organs of sense and of certain 
important secretions. It consists of two principal layers, the 
epidermis (epithelium, cuticle) and the corium (derma, cutis, 
or true skin). The epidermis is very thin as compared with 
the true skin which it covers, and is entirely removed prepara- 
tory to tanning ; it nevertheless possesses important functions. 
Its inner mucous layer, which rests upon the true skin, is soft 



HIDES AND SKINS 49 

and composed of living nucleated cells, which multiply by di- 
vision and form cell-walls of keratin. These are elongated in 
the deeper layers, and gradually become flattened as they ap- 
proach the surface, where they dry up and form the horny 
layer which is being constantly worn away, thrown off as dead 
scales of skin, and renewed from below by the multiplication 
of the cells. 

It is from the epithelial layer that the hair, as well as the 
sweat and fat-glands, are developed. Each hair is surrounded 




Figure 34. — Cross-section of calfskin. 



by a sheath continuous with the epidermis, and in which the 
young hair usually grows as the old one falls out. Near the 
openings of the hair-sheath upon the surface of the skin the 
ducts of the sebaceous or fat-glands pass into the sheath, and 
secrete a sort of oil to lubricate the hair. The base of the hair 
is a bulb, enclosing the hair papilla, which is a projecting knob 
of the true skin, and which, by means of the blood-vessels 
contained in it, supplies nourishment to the hair. The hair 
bulb is composed of round soft cells, which multiply rapidly, 
and, pressing upward through the hair-sheath, become hard- 
ened, thus increasing the length of the hair. 

The process of development of the sudoriferous or sweat- 
glands is very similar to that of the hair. They consist of 
more or less convoluted tubes with walls formed of longitudi- 



50 PRACTICAL TANNING 

nal fibers of connective tissue from the corium, lined with 
a single layer of large nucleated cells which secrete the 
perspiration. 

Besides the hair, and hair-sheaths, and the sebaceous and 
sudoriferous glands, the epidermis layer produces other struc- 
tures of a horny character, including horns, claws, and nails, 
which, both chemically and anatomically, are analogous to ex- 
aggerated hairs. This is apparent in the quills of the porcu- 
pine. The whole of the epidermis, together with the hairs, 
is separated from the corium by an exceedingly fine membrane 




Figure 35. — Cross-section of cowhide. 

called the "hyaline" or glassy layer. This forms the very thin 
grain surface of tanned leather, which is of a structure dif- 
ferent from the rest of the corium. 

The structure of the corium or true skin is quite different 
from that of the epidermis. It is composed principally of in- 
terlacing bundles of fibers known as "connective tissue," and 
cemented together by a substance more soluble than the fibers 
themselves. These fiber bundles are loosely interwoven in the 
middle portion of the skin, but become compact again near 
the flesh. The outermost layer, just beneath the epidermis, is 
also very close and compact. The skin is united to the ani- 
mal by a network of connective tissue (pannicnlus adiposus), 



HIDES AND SKINS 



51 



which is frequently full of fat cells and is then called "adipose 
tissue." This portion, together with some actual flesh, is re- 
moved in the process of fleshing. 

Ordinarily, the corium or true skin is the only portion used 
for leather. To obtain it in a suitable condition for the vari- 
ous tanning processes, the hair or wool, together with the 
epithelium, must be completely removed without damaging the 
skin itself; and special care must be taken that the grain, or 
portion next the epidermis, does not suffer injury during the 




Figure 36.— Cross-section of calfskin, (a) Corne- 
ous layer, (b) malpighian layer, (c) papil- 
lary layer, (d) reticular layer, (e) hair 
shaft, (f) hair follicle, (g) sebaceous gland, 
(h) hair, (i) inner root-sheath, (o) outer 
root-sheath. 

treatment. Figure 36 shows a cross-section of a calfskin five 
weeks old, prepared by Geo. D. Rosenthal. 



Butt, 


Shoulder, 


per cent 


per cent 


4.14 


5.16 


12.31 


16.74 


4.81 


2.29 


58.83 


39.66 


19.91 


36.15 



52 PRACTICAL TANNING 

Samples were taken from various parts of the skin, .which 
on analysis gave the following results : 

Belly, 
Constituent percent 

Coagulable protein 4.30 

Elastin 19.43 

Mucoid 1.24 

Collagen 51.46 

Keratin 25.73 



A very exhaustive study of hide structure was conducted 
by Dr. Rosenthal, the result of which appears in the 1917 vol- 
ume of the American Leather Chemists' Association. 

Conservation of skin substance. — It must appear evident 
to anyone engaged in the hide and skin business that there is 
continual loss of substance and depreciation of value in a skin 
from the moment it is taken off the animal until it is finally 
converted into leather. The principal reason for this loss is 
the presence of liquefying bacteria, which bring the gelatine of 
the skin into solution. The conservation of this material is 
of vital interest to the tanner, and should also demand the at- 
tention of the skin collector and dealer. With this end in view, 
experiments were conducted for a number of years to dis- 
cover some inexpensive method of conserving the substance 
of skins, especially calfskins, without any detrimental effect. 

Of all the materials tested, zinc chloride has been found to 
prevent this liquefaction best, and consequent loss and deteri- 
oration without producing any results, visible either in 
the skin or in the finished leather, that are in any way 
objectionable. 

Zinc chloride. — The method of using zinc chloride, which 
has given the most satisfactory results, is as follows: The 
fresh skins are first salted in clean, coarse salt for the pur- 
pose of withdrawing the blood from them, and are allowed 
to remain in a low, narrow pile for 24 to 48 hours. They are 
shaken out of this first salt, which is taken to the refuse pile 
and thereafter used only for salting the trimmings, and placed 
in a pack, and to the salt which is used for this second salting, 



HIDES AND SKINS 53 

zinc chloride is added. For convenience, a stock solution is 
made of 1 lb. of zinc chloride to 1 gallon of water. To a bar- 
rel of water, add 1 pint of this solution, and stir thoroughly. 
The salt intended for the second salting is sprinkled with this 
zinc chloride solution until a quantity, taken in the hands 
and pressed, oozes moisture. The salt, treated as above, is 
thrown on the skins in the usual way. Fresh skins treated 
in this manner lose practically no gelatine and remain fresh 
and clean as long as skins are ordinarily kept. The treatment 
is also valuable in conserving skins that are shipped in. In 
a case where skins show a tendency to hair-slipping or have 
become heated, it is advisable to dip them first into a solution 
of the zinc chloride made by adding 1 pint of the stock liquor 
to a barrel of water, and salting as directed for the second 
salt. The results obtained from handling hair-slipped skins 
in this manner are remarkable. The zinc chloride instantly 
checks the liquefaction of the bacteria, and the leather pro- 
duced from the skins is the equal of that made from perfect 
ones. Comparative experiments with cold-storage methods 
have also been made. One lot of skins was kept at a tempera- 
ture of 30° F., another at 0° F. ; at the same time, skins were 
put in pack by the zinc chloride method, and all were held for 
one year. Those treated in zinc chloride were in every way 
equal to those kept in cold storage; and the leather produced 
from the zinc-chloride treated skins was equal to that made 
from strictly fresh stock. 

A general following-up of • the above suggestions will do 
much toward conserving the most valuable constituent of the 
raw skin. The method is not an expensive one, zinc chloride 
costing only about 30 cents a pound. 

Formaldehyde. — The antiseptic and germicidal action of 
this substance has long been known in medicine and found of 
practical use, and its application for the preservation or dis- 
infection of raw skins is therefore only natural. With its aid, 
skins that have already undergone putrefaction may be steri- 
lized, as well as such as it is feared may decompose during in- 
terruption of the usual process. To effect this, for each 100 



54 PRACTICAL TANNING 

parts of the soak water, take 2 parts of 40 per cent formalde- 
hyde, and use this solution for 6 to 8 days, when it should be 
strengthened by the addition of a further 2 parts of formalde- 
hyde. Dried skins should be merely soaked for 10 minutes in 
a solution of formaldehyde of 4 per cent strength, after which 
they should be laid in piles for 12 hours, and finally dried in 
the air. 

In 1902, Roberts, of Buenos Aires, patented a process by 
which skins were subjected to the action of antiseptic gas — 
that is, formaldehyde — for a time in order to preserve them. 
The Conservadore Mercantile Co. of that city, according to 
this patent, submitted skins after flaying and before salting 
to the action of formaldehyde vapors in closed chambers. This 
destroyed the putrefactive elements which were likely to be 
present in the skins and sterilized them for a certain time; 
finally the skins were salted and dried out. 

Salting by itself does not sterilize skins permanently; it can 
only retard and diminish the development and the activity of 
the putrefactive organisms. The damage known as salt stains 
is said by some investigators to be caused by micro-organisms 
which resist the action of salt, and it may be presumed that a 
treatment with formaldehyde would greatly reduce this form 
of damage. Also, for skins which are preserved by means of 
drying, formaldehyde may be of excellent service, the goods 
not being exposed to the risk of decomposition setting in dur- 
ing drying. Moreover, the pungent odor of the formaldehyde 
repels flies and other insects, which, under other circum- 
stances, are attracted to the skins during the drying process, 
and thus the presence of larvae in the goods is very likely pre- 
vented. Finally, it is possible by this means to disinfect the 
skins from carrying disease germs, especially from places 
which are often subject to this sort of danger. Complete dis- 
infection by means of formaldehyde entails a very strong ac- 
tion, and this causes several difficulties in the work of soaking, 
liming, etc., which are nevertheless surmountable. In any 
case, it is only recommended that this process be employed for 
skins which have undergone slight putrefaction, and for 



HIDES AND SKINS 55 

those in which mere salting would not suffice for perfect 
preservation. The strength of the solution should never ex- 
ceed 5 per cent, as otherwise the skin substance will be greatly 
hardened. If the skins are to be salted, they should not be 
treated, previous to the salting, with a solution of formalde- 
hyde, because they would absorb too much water, for the' re- 
moval of which an excessive quantity of salt would be re- 
quired. It is therefore necessary in this case to use formalde- 
hyde in the gaseous form and not as a solution. 



CHAPTER II 



SOAKING 



The processes that precede the actual tanning or conversion 
of hides into leather are about the same for all classes, whether 
the tannage be chrome or vegetable. The object of these proc- 
esses is to bring the hide to the natural soft condition it 




Figure 37. — Pin-mill, wash-wheel, or drum for washing fresh hides. 

is in when removed from the animal's back, and in addition, to 
remove the blood, manure, dirt, and salt. 

Fresh or market hides. — This grade of hides, after having 
been trimmed, simply requires washing to remove the blood 
and dirt, and is usually accomplished by milling for about 
a half-hour in cold, running water, using a pin-mill or drum 
as shown in figure 37. 

56 



SOAKING 



57 



This treatment is absolutely necessary, as the adhering 
blood, lymph, and dung, would soon set up putrefaction, with 
subsequent damage to the stock. 

Green-salted hides. — The hides are first trimmed — the 
tails, shanks, and pates being cut off in the hide cellar — and 
are then soaked. One of the most approved methods of soak- 



'-■it* 


■fly l^s|||L 


: ,, j 


'^- : ' 



Figure 38. — Washing hides preparatory to soaking. 

ing is to hang the hides in the water, which should be soft and 
clean. If the water is hard, 1 lb. of borax for each 100 gal- 
lons of water, dissolved in hot water, should be stirred into 
it to make it softer, and increase its softening and cleansing 
powers. The hides should be hung in the water, from tail to 
head, and left therein for 24 hours; they are then usually 
taken out and cut into halves or sides. The water in the soak 
vat is run out and fresh water run in, when the sides are put 
back and soaked 24 hours longer. Splitting into sides can 
also be done after the second soaking. The object of the 
soaking process is to soften the hides and remove the salt, 



58 PRACTICAL TANNING 

dung, blood, and dirt adhering to them. It is important that 
this be done quickly and thoroughly, so that the hides may go 
into the lime clean and soft, yet retaining their substance in- 
tact. Prolonged soaking of salted hides results in a loss of 
gelatine and in loose and spongy leather. On the other hand, 
if the hides are not soaked long enough, they do not go into 
the lime in the right condition, and the grain may have serious 
defects. It is usually best to change the water once during 
the process. If the hides are very dirty, two changes are 
necessary; if only slightly salty and dirty, one change is suf- 
ficient. Figure 38 shows the stock out of the wash-wheel 
and ready for soaking. 

No exact rule for soaking can be given, as much depends 
upon the thickness and condition of the hides and the temper- 
ature of the water. Usually, however, ordinary hides are 
sufficiently soaked by being hung in water 24 hours, then re- 
moved and re-soaked another 24 hours. At the end of the 
soaking process the sides are drained, fleshed, toggled together 
in a chain, and passed into lime. 

A common procedure for green-salted hides is to throw the 
trimmed stock into fresh water for 24 hours, and then mill for 
a half-hour in cold running water, when they are fleshed and 
ready for depilation. 

Dry-salted hides. — Those that have been dried after salt- 
ing require a longer soaking to restore the natural soft condi- 
tion. This is usually accomplished by soaking for 24 hours 
in water to which 0.2 per cent of caustic soda has been added. 
The hides are then removed from the soak and milled in run- 
ning water for a half-hour. They are then cut into sides and 
returned to the soaks for another day, when they are dry- 
milled for half an hour, fleshed, and piled-down over night. 
If not thoroughly soaked, they are returned to the soaks for 
another day. 

Dry hides. — Those that are received by the tanner in flint- 
dry condition require longer soaking and more thorough work- 
ing in order to get them into the soft, pliable condition which 
is necessary before they can be fleshed and limed. The follow- 



SOAKING 59 

ing method of soaking dry hides usually proves satisfactory: 
For every 100 gallons of water in the vat, dissolve 1 lb. of 
sodium sulphide or -J lb. of caustic soda in hot water, and 
pour the solution into the water, plunging thoroughly. Put 
the hides into the water and let them soak 24 hours. At the 
end of that time take them out of the water, put them into a 
dry mill, and run them in it 30 minutes; next place them in a 
pile or piles, covered up, and let them lie 24 hours; then put 
them back into the water from which they were taken and let 
them soak 24 hours longer. From this soaking, .run the hides 
in the dry mill for a half-hour; then flesh them. After flesh- 
ing, place in clean, cold water over night ; then lime them. 




ff\ 



Figure 39. — Fulling stocks. 

Formic acid is sometimes used in soaks to hasten the soften- 
ing of dry hides, 1 lb. of the acid being added to each 100 
gallons of water in the soak vat. The hides are first placed in 
clean water for a day or two, and then hung in the acidified 
soak. If they swell excessively, some salt should be added to 
check the swelling. After the hides have been soaked two 
or three days, they should be washed and placed in clean 
water for a few hours and then placed in the lime. ■ 

Stocks. — In softening flint hides, some tanners resort to the 
use of the stocks, or kickers, after the preliminary soaking. 
This mechanical working takes the place of "breaking over," 
which was formerly accomplished on the beam with a blunt 
knife. The stocks shown in figure 39 consist of a curved 



60 



PRACTICAL TANNING 



metal or wooden box, in which two heavy hammers work 
backward and forward on a cam, thus driving the hides against 
the walls on either side. The treatment of hides by this 
method is rather strenuous, and is being replaced by the drum 
in most tanneries. 

Fleshing. — In order to facilitate the depilation, hides and 
skins are usually fleshed before entering the depilating liquor, 
or may be so treated to assist in the soaking operation. This 
fleshing consists in removing the excess of flesh or fat on the 
under side of the hide, and may be accomplished over the beam 
with a sharp knife or by means of machinery built for the 
purpose. Figure 40 shows one of the many forms of such 




Figure 40. — Turner pneumatic fleshing machine. 



machines. It consists essentially of a spiral knife against 
which the stock is forced by means of a heavy rubber-covered 
roll. The machine may be adjusted to suit the thickness of 
the hide and so regulated as to take off a light or deep cut as 
desired. 

Putrid soaks. — At one time the use of putrid soaks was very 
common, but the modern tanner realizes that putrefaction 
means loss of hide substance; and as he wishes to conserve 
his hides as much as possible, this wasteful and dangerous 



SOAKING 



61 



method has been almost entirely abandoned. Figure 41 shows 
a pack of hides out of soak, and ready for depilation. 

Chemical soaks.- — Various chemical products for hastening 
soaking have been placed upon the market. They are all either 
alkalies or alkaline salts, and have no advantage over sodium 
sulphide or sodium hydroxide (caustic soda) ; in fact, expe- 




Figure 41. — Hides ready for depilation. 

rience has shown that of all softening agents .the latter is the 
most satisfactory. For dry hides or kips, a 0.2 per cent solu- 
tion of this chemical will reduce the time of softening for 
even flint hide to about two days. 

Butyric acid has been suggested as a softening agent, in 
which case from 3 to 5 oz. are used for each 100 lb. of stock. 
The advantage derived is that no hide substance is lost. It 
has never, however, met with popular approval. 

Paddle soaking. — In pit soaking, the stock is likely to pack 
at the bottom, and thus be prevented from absorbing water 
uniformly. To overcome this, the hides are drawn and thrown 



62 PRACTICAL TANNING 

back. By means of a paddle, the labor involved in handling 
the stock is obviated, and by simply running the paddle at five- 
minute intervals twice a day, the hides may be loosened up 
and the position quickly changed. The use of a paddle is 
especially advantageous for green-salted or market hides. 

Kips. — The same methods as applied to hides hold equally 
good for kips. As this grade of raw stock is used for the 
same purposes as light hides, the processes employed need no 
further elaboration. 

Calfskins. — One of the most important processes through 
which calfskins are passed before they are tanned into leather 
consists in soaking, which cleanses and softens them. There 
are also mechanical and manual operations, such as trimming 
and fleshing to remove the superfluous and objectionable parts. 

Green-salted skins. — The soaking of green-salted calfskins 
should be done in clean, fresh water. As good a method of 
soaking as any is to shake the skins free from salt, trim off 
the useless portions, and then put them into the water for 24 
hours. The remaining salt and dirt are next removed by 
washing the skins for 15 minutes with running water. Light 
skins are then fleshed and put through a liming process. Heavy 
skins are re-soaked 12 hours and then passed into the lime 
liquors. 

Dry skins. — Calfskins that are received at the tannery in a 
hard, dry condition require thorough softening before they can 
be limed and unhaired. Caustic soda is an effective softener 
for such skins. . Dissolved and added to the water in which 
the skins are soaked, it hastens the softening and freshens up 
the withered fibers and grain; 1 lb. of the alkali is used for 
each 100 gallons of water in the paddle vat. When the skins 
have become flexible in the soak they should be taken out and 
run dry in a drum for half an hour, then put back into the 
water and soaked 24 hours longer. If they are not perfectly 
soft at the end of that time, they should be placed in piles over 
night and then re-soaked in clean water for 24 hours. They 
are next trimmed and fleshed, and put into the lime. 

In place of caustic soda, formic acid and salt may be used 



SOAKING 63 

in the soaks. For 100 parts of skins, 5 parts of the acid are 
used in 1000 parts of water; some salt may advantageously 
be added. This process takes from 2 to 5 days, according to 
the substance and condition of the skins. The softening can 
be hastened by running the skins in a drum, but this should 
never be done until they are soaked through and fairly pliable 
in the soak. Upon coming from the acid soak, the skins are 
fleshed and then put into the lime solutions. 

Sheepskins. — In the soaking of sheepskins previous to the 
removal of the wool, the tanner or the wool-puller has not only 
to consider how the skin can best be brought back to its natu- 
ral soft condition, but it is also necessary for him to consider 
the effect the method of soaking adopted may have upon the 
quality of the wool, since it may be greatly depreciated in 
value by using the wrong materials to aid the softening of 
dry sheepskins. In the case of skins received direct from the 
butcher, all that is required before the depilatory paint is ap- 
plied is to remove adhering dirt and blood by washing or 
soaking in water. Simple treatment in this way for a short 
time has no effect whatever upon the wool, but prolonged 
soaking may remove much of its peculiar natural fat, which 
should be retained, as otherwise the wool loses weight, and 
felting is liable to take place, the luster of the wool being 
also diminished. 

Fresh skins. — For fresh skins, the method recommended is 
to shake them free from adhering salt, and then place them 
in fresh soft water to remove salt, blood, dirt, etc. They may 
then, if necessary, be transferred to fresh water for a few 
hours, after removing any clotted dirt and blood by beating or 
breaking over the beam. They are then drained and treated 
for the removal of the wool. 

Dry skins. — In the soaking of dry pelts, something must 
be used to shorten the time required for bringing the skins 
back to the original soft condition. Of the alkalies com- 
monly employed in soaking hair skins, few can be used on 
sheepskins because of their injurious effect upon the wool. 
The wool fats are saponified by the alkalies, and removed, 



64 PRACTICAL TANNING 

leaving the wool brittle and less elastic, and also injured as 
regards luster. Caustic soda and sodium sulphide will, in a 
fairly weak solution, completely dissolve the wool in a few 
minutes, and therefore cannot be used as softening agents; 
neither can caustic potash and washing soda be employed. 
Ammonium carbonate and borax are the alkalies which have 
the least effect upon wool. If the former is used, the skins, 
when placed in lime, will become impregnated with calcium 
carbonate (lime blast) unless the ammonium carbonate is first 
entirely removed by washing. 

Borax may be employed in weak solutions, using 1} lb. to 
100 gallons of water; but in stronger solution it also tends to 
dissolve the natural grease of the wool. It is not advisable to 
use acids in the soaks, because of their swelling action on the 
skin. Sulphurous and formic acids, preferably the latter, may 
be employed in extremely dilute solutions. These acids are 
more or less dangerous, however, in the hands of careless and 
incompetent workmen. Acids are therefore not generally rec- 
ommended on account of their action on the pelt. 

Of the various soaking agents that might be used, sodium 
bisulphite has been found to give the best results, without in- 
jury to either skin or wool. This substance, which is best 
used in the solid form, is only slightly acid, so that there is 
no danger of swelling the pelt except in comparatively strong 
solutions. It is inexpensive, and only a small quantity is 
required for effective soaking. The wool is improved in color 
by the bleaching action of the sulphur dioxide present; and its 
quality, so far as strength, luster, and elasticity are concerned, 
is in no way impaired. Sodium bisulphite also acts as an an- 
tiseptic, preventing the growth of micro-organisms which 
would produce decomposition of the skin with its consequent 
loss of skin substance. 

According to the Tanner's Year Book, the strength of bisul- 
phite solution that has been found to give the best result in 
the soaking of sheepskins is 1 lb. of dry commercial sodium 
bisulphite per 100 gallons of water. The dry skins are placed 
in this solution, and allowed to remain therein until they are 



SOAKING 65 

soft enough for breaking over the beam. After breaking, 
they are transferred to fresh water to complete the softening, 
and then treated in the usual way. Very hard skins may be 
given a second treatment in the solution of sodium bisulphite. 

Although bisulphite has an antiseptic action, the subsequent 
removal of the wool is not prevented, and whatever disadvan- 
tages it possesses may be easily overcome. 

Green-salted sheepskins. — Clean water should be used. In 
warm weather, 10 or 12 hours is generally sufficient time; but 
in cold weather the skins may be soaked longer without in- 
jury. When the skins have become soft and clean they have 
been soaked enough. They should then be removed from the 
water, and thrown over horses or otherwise allowed to drain 
for several hours, or they may be passed through an extractor 
and the surplus water removed from them. They should be 
clean and soft before any depilatory is applied to them. 

Dry sheepskins. — Sodium bisulphite is of much assistance 
in soaking dry sheepskins. As stated above, it also acts as an 
antiseptic and prevents the growth of micro-organisms which 
would produce decomposition and loss of skin substance. One 
pound of commercial sodium bisulphite is used for each 100 
gallons of water in the soak vat. The dry pelts are placed in 
the prepared soak, and allowed to remain therein until they are 
flexible and can be broken over the beam. After they have 
been either broken over the beam or drummed, for a short 
time, they are put into a fresh soak to complete the softening, 
and are then treated in the usual way. Very hard skins usu- 
ally require a second soaking in the sodium bisulphite solu- 
tion. Ordinary skins become sufficiently soft in 24 hours. It 
is always advisable to place the skins in fresh water a few 
hours after they have been softened to remove the sodium 
bisulphite, as well as the last traces of salt and dirt. It is 
also good practice to use fresh solutions of the chemical for 
every two or three packs of skins. The next process is re- 
moval of the wool. 

Goatskins. — It is very important that dried and dry- 
salted skins should be thoroughly softened and cleansed be- 



66 PRACTICAL TANNING 

fore they are put into lime liquors. Dried skins should be 
soaked separately from dry-salted stock; and to get them soft- 
ened in the shortest time possible, and the fibers and grain 
freshened and cleansed, some caustic soda or sodium sulphite 
should be added to the water, and revolving drums used as 
soon as the skins become flexible in the water. 

Dried skins. — The most efficient way to soak dry goat 
skins is by the use of what is known among tanners as the 
sulphide soak. This is prepared by adding 1 lb. of sodium 
sulphide dissolved in hot water, to the water in the soak vat, 
this quantity being sufficient for 100 gallons of water. If 
the skins are heavy, and very hard and dirty, 2 lb. of the 
material should be used. The skins are placed in the pre- 
pared soak, and are left therein from one day until the next ; 
they are then drummed in running water for a short time to 
soften and cleanse them further. From the drum they are 
placed in a clean soak, containing, like the first, 1 lb. of sodium 
sulphide or caustic soda for each 100 gallons of water. The 
next day they are taken out and drummed again in running 
water. It is good practice then to shut off the water, and run 
the skins dry in the drum for 15 minutes, after which they 
should be placed in clear water until the next day. Some 
skins require longer soaking and more drumming than others. 
More or less sodium sulphide may be used, according to re- 
quirements of the skins, an excess doing no harm. If it is nec- 
essary to leave the skins in the last clear soak for some time 
before liming them, 1 lb. of carbolic acid for each 100 gal- 
lons of water should be added to prevent decomposition, the 
acid being washed out in running water before depilating. 

Dry-salted skins. — The softening of this class of stock is 
accomplished by soaking them in a sulphide soak over night, 
next drumming them in running water, and then re-soaking 
them in a second sulphide soak for 24 hours. These skins 
require thorough drumming in running water to rid them of 
every trace of salt. Skins that were pulled off the animal 
should be cut open after they are soaked and all skins should 
be trimmed before they are put into lime. 



SOAKING 67 

Sodium bisulphite. — An efficient soak for dry stock is pre- 
pared by adding 1 lb. of sodium bisulphite to every 100 gallons 
of water in the vat, as already described for sheepskins. The 
skins are placed in the soak, and when they have become flexi- 
ble, they are run in a drum and soaked again in a bisulphite 
liquor, then washed and limed. 

Kangaroo skins. — On account of the practical exhaustion 
of kangaroo (wallaby) skins, the manufacture of this type 
of leather has greatly diminished in recent years. Kangaroo 
skins are characterized by great suppleness, toughness, and 
thick grain. The leather is very compact and resists the pen- 
etration of moisture, and does not readily crack or peel off. 
On account of its distinctive qualities it is a splendid shoe 
material — in a class by itself — and is especially suitable for 
shoes for tender feet. Excellent leather is made by tanning 
the skins by a chrome process; also by tanning with quebracho 
or gambier. Dull-finished kangaroo leather has long been a 
favorite material for the tops of shoes, and glazed leather for 
vamps. 

Soaking and softening. — Kangaroo skins come from Aus- 
tralia, and are received by the tanner in the dry condition. 
It is necessary to use some chemical in the soaks, such as 
borax, sodium sulphide, or caustic soda, to hasten the soften- 
ing, and to bring the goods to as near the natural soft condi- 
tion as possible. From 1 to 2 lb. of any of these chemicals 
may be used for every 100 gallons of water in the vat. When 
the skins have become pliable, they are taken out of the soak 
and drummed some time, then re-soaked until they are thor- 
oughly softened. The soak readily softens the skins and 
freshens up the dried and withered grain. The loosened flesh 
should be removed before the skins are put into lime. 

Borax also softens the water and hastens the soaking of 
the skins, 5 or 6 lb. being sufficient for 1000 gallons of water. 
Dissolve with hot water; pour the solution into the soak and 
stir thoroughly; then throw in the skins. 

Pigskins. — From time immemorial these have been used for 
many purposes; at the present time they are employed more 



68 PRACTICAL TANNING 

extensively than ever. When properly tanned, they are as 
durable as goatskins, as pliable as calfskins^ and present a 
peculiarly attractive appearance. They are finished in russet 
and colors, and are used for inner-soling, saddles, traveling- 
bags, pocketbooks, belts, jewelry cases, bookbindings, sport- 
ing goods, shoes, slippers, suspenders, leggings, military equip- 
ments, trusses, wall decorations, screens, for upholstering, 
and for carriage and automobile trimmings. Various ways of 
tanning them will be described later. 

Washing. — Pigskins contain a grease that has to be elim- 
inated before they are limed, or the leather will be greasy 
and hard. After having been scraped out dry before soak- 
ing, the skins are washed in a warm solution of sal soda 
(sodium carbonate). Put about 5 lb., of sal soda into a barrel 
of water heated to 95° F. Put the skins in one at a time, 
and leave them in long enough to get soaked through, 
and then put them on the beam and strike them out thorough- 
ly with a dull knife, bearing on hard and forcing out as much 
of the grease as possible. This should be done two or three 
times. The skins are then rinsed off in warm water and 
soaked several hours in cold water before they are de-haired 
and limed. A great deal of grease can be forced out by thus 
passing them through the warm solution of sal soda and then 
working them out on the beam. The skins are next soaked, 
fleshed, and de-haired. 

De-greasing. — In recent years, pigskin and other stock con- 
taining a large amount of grease, have been de-greased with 
various solvents. One of the simplest methods consists in 
running the pickled stock with kerosene, using about 3 gal- 
lons for each 100 lb. of skins. After running the stock with 
this material for about one hour, the kerosene is washed out 
with salt water, finally finishing with a weak pickle solution. 
A more effective de-greasing mixture is manufactured by the 
Vacuum Oil Co., and is being used in considerable quantities. 

Krouse Process. — A process for de-greasing sheep and pig- 
skins has been patented by C. E. Krouse, and consists in treat- 
ing the dry pickled skins with high test gasoline in specially 



SOAKING 69 

built containers. The solvent is pumped into the cylinder con- 
taining the skins, where it remains for a definite length of 
time. The solvent now carrying the removed grease is trans- 
ferred to a special form of still, where, by distillation, the sol- 
vent is removed for further application, while the grease from 
the skin is recovered, and may be used as crude soap stock 
or employed for other purposes. 

Furs and hairskins. — Although the tanner, as a rule, is 
not interested in the tanning of furs, there are occasions when 
he does want to preserve the pelt in its natural hair cover. 

Soft, green-salted skins to be tanned with the fur or hair 
on them require but two or three hours' soaking in clean water 
to become soft and clean. Dry skins are soaked and softened 
most effectively in water to which borax, caustic soda, or 
formic acid has been added. A solution of 2 lb. of borax in 
100 gallons of water is a suitable soak for dry skins. Well- 
cured skins can be softened in a soak consisting of 100 gallons 
of water to which 1 lb. of caustic soda has been added. An. 
excellent soak is also prepared by adding 1 to 2 lb. of formic 
acid to 100 gallons of water. This is an approved method 
of soaking, since the acid has antiseptic properties, and will not 
allow decay to take place. The water used for soaking should 
always be fresh and clean ; and the soaking should be done as 
quickly as possible, to avoid decomposition and loosening of 
the hair. When soft and clean, the skins are fleshed, and all 
lumps of fat and flesh removed. The skins should next be 
washed in a warm solution of soft soap, which makes the 
hair and the skin itself clean and free from grease; they are 
then ready to be tanned. 

Another method of preparing the skins is as follows : They 
are taken in raw condition, and beamed and scraped on the 
flesh side until they are free from flesh and greasy matter. 
They are not soaked at first. Softening is done with wet saw- 
dust. Soak some sawdust in water; spread the skins out 
smooth 1 , flesh side up, and spread the wet sawdust an inch deep 
on the flesh side, and let them lie until they are softened. 
In the case of greasy skins it is necessary to soak them in 



70 PRACTICAL TANNING 

borax water, and then wash them in warm sal soda solution, 
omittinsr the sawdust treatment. When soft, fleshed, and 

o 

clean, the skins are ready to be tanned. 

Formaldehyde raw stock. — It often- happens that formal- 
dehyde is used as a preservative and disinfectant on skins, but 
this chemical has a hardening effect on the fibers. For skins 
partly disinfected by means of formaldehyde this does not 
present any great difficulty, especially when the skins have 
been salted, as the salt has penetrated throughout so that they 
are not hardened at all. For dried skins treated previously 
with formaldehyde it is necessary to add some activating sub- 
stance, such as formic acid or sulphurous acid, to the soak 
water. Naturally, this method of working is not without dis- 
advantage as regards the quality of the glue stock, for it is 
well known that one cannot obtain as good a quality of such 
stock; but, of course, the main consideration for the tanner is 
to obtain good leather, and although the value of the glue 
stock is not negligible, it is not the principal thing to consider, 



CHAPTER III 

DEPILATION 

Having brought the stock to a soft and perfectly clean con- 
dition, as described in the previous chapter, the next step, 
usually, is the depilation or removal of the hair and epidermis. 
Accompanying depilation there is generally a swelling action 
caused by the chemicals used, which makes the fibers separate, 
and at the same time more or less of the cementing material 
is dissolved. The natural fats occurring in the hide or skin 
are also affected during depilation, being converted into solu- 
ble and insoluble compounds, which are very largely removed 
during the working processes. 

Hides that have been improperly cured often present what 
is known as hair-slips; that is, the hair falls out in patches, 
and is likely to be accompanied by a damaged grain. The cause 
of this slipping is putrefaction, the stock having become wet 
in these spots, or perhaps locally overheated during 
transportation. 

Sweating. — The oldest method of depilation seems to have 
been by means of incipient putrefaction, or as it is called, 
"sweating." The hides were allowed to remain in piles in a 
warm, damp room until the mucous matter connecting the epi- 
dermis with the dermis had decomposed, which thus loosened 
the hair without injuring the true skin. This method, how- 
ever, often resulted in damaged stock, and so the process was 
improved by allowing the hides to hang in a closed, damp room 
or cellar called a "sweat-pit." Two general methods are em- 
ployed, known as "cold sweat" and "warm sweat." 

Cold sweat. — This method is still used in America to some 
extent, especially for de-hairing dry hides for the manufac- 
ture of sole leather. The sweat-pit is a structure usually built 
above ground, and protected from outside atmospheric influ- 
ences by means of a double wall between which is a filling of 
tan bark or other material to prevent loss of heat by radiation. 

71 



72 PRACTICAL TANNING 

The temperature of these pits is controlled by means of steam 
pipes running under the false flooring and a sprinkler system 
to provide moisture and lower the temperature if necessary. 
The temperature is maintained at about 70° F. The hides are 
hung on hooks, each chamber holding a single pack. The 
sweating usually lasts 4 or 5 days. Near the end of the opera- 
tion the stock is carefully examined, and those hides showing 
the first signs of slipping are dropped to the floor in order to 
retard putrefaction, it being cooler on the floor than higher 
in the pit. At the end of the process the hides are thrown into 
lime liquors for a short time in order to remove the slimy 
feel, and to plump the stock slightly. The value of this process 
depends upon the fact that the hides are left in a firm condi- 
tion without any appreciable loss of hide substance, but even 
if most carefully conducted there is great danger from ex- 
cessive putrefaction, with resultant damage to the grain. 

Warm sweat. — The warm-sweat method is very similar to 
the cold-sweat process, except that a higher temperature, about 
80° F., is used, and the time of treatment is somewhat shorter. 
It is applied more especially to sheepskin and is known as 
"staling." This process is not employed to any extent in the 
United States. 

Liming. — The first chemical method of depilation was that 
in which slaked lime was employed. Although this material 
has been used for many years, the methods of application do 
not differ materially from those in vogue a century or more 
ago. Lime used for de-hairing must be as free as possible 
from magnesia, clay, or iron, as these materials not only 
diminish the lime content, but cause the lime to slake with 
much more difficulty; and the iron, being insoluble, becomes 
fixed in the grain, with subsequent production of stains. 

Quicklime. — The natural source of lime is limestone, in 
which it occurs in combination with carbon dioxide, and is 
known chemically as calcium carbonate. There are other nat- 
ural forms of calcium carbonate, such as chalk and marble. 
In order to make pure lime or calcium oxide (CaO), lime- 
stone or chalk is heated in a kiln to a high temperature, when 



DEPILATION 73 

the carbon dioxide (CO2) is driven off, leaving what is known 
as quicklime, according to the reaction : 

CaC0 3 +heat=CaO+C0 2 

On coming in contact with water, quicklime combines read- 
ily with it, forming calcium hydroxide or slaked lime. In do- 
ing this, the water should be introduced slowly, and the mass 
well stirred after each addition. During the slaking a great 
deal of heat is generated, and the lumps of lime fall to a pow- 
der. When properly slaked, the resulting product should as- 
sume the appearance of a smooth paste. It is necessary to se- 
cure proper slaking, otherwise the unaffected lumps will col- 
lect in pockets and cause serious damage to the stock. 

Hydrated lime. — By the careful addition of just sufficient 
water to bring about the reaction between lime (CaO) and 
water (H2O), a dry powder may be produced according to the 
following reaction : 

CaO+H 2 0=Ca(OH) 2 

» 
This powder is now being largely used by the tanner, and 

is known as hydrated lime. The advantage of this material 
is that it may be kept indefinitely without change, and may 
be used in the process of depilation without fear of damage 
to the stock. 

Attention should be directed to a statement which is often 
made, that, owing to the limited solubility of lime in water 
(1.3 parts per 1,000 at 70° F.), there is no danger of de- 
stroying a pack of hides or skins by using an excessive amount. 
This is misleading. There is probably no danger of destroy- 
ing the stock, but there is great danger of damaging it by 
improper lime treatment. That lime can be and is used 
in various ways is proved by the fact that if we visited 
100 tanneries we would find no two plants using the same 
method of liming. Yet lime is a compound which is only 
slightly soluble in water, and according to theory, its beneficial 
effects can only come from what goes into solution ; and pro- 
viding that we always have an excess present, the results 
should always be the same, no matter how much we may care 



74 PRACTICAL TANNING 

to use. This is a case where theory and practice do not 
coincide. 

Many tanners claim that in de-hairing a hide properly it 
is necessary first to treat the stock with old lime liquors, and 
gradually bring the hides into fresh lime solutions. There 
is some foundation for this belief, but there are limitations 
which must be observed. There is no doubt that old limes 
do have a 'softening effect upon dry hides, due to the putre- 
factive action of the bacteria which they contain, as it has 
been shown that putrefactive bacteria are present in old limes. 
That they subsist upon mucous matter between the epidermis 
and dermis as well as upon the connective material between the 
fibers has also been shown. 'But are we sure that they care 
only for the mucous matter and connective material ? We are 
not safe in assuming that they will attack these materials only, 
for they will also act upon the fibers or gelatinous matter. 
Would it not be better to depend upon the soaks for securing 
the soft condition we desire, and not upon the uncertain action 
of putrid lime? 

It is claimed by some tanners that it is impossible to de-hair 
with fresh limes, but those who make such a statement have 
evidently never tried to do so. It is not the intention, how- 
ever, to try and convert those who are using putrid limes, but 
rather to give some of the salient points which have devel- 
oped as the result of a series of tests extending over several 
years, and which were carried out at the suggestion of the 
National Association of Tanners. The points that have been 
paramount in all of these investigations were the determina- 
tion of weight, measurement, and the condition of the leather 
obtained when the various well known and commonly used 
depilating agents were employed. In conducting the experi- 
ments, actual working conditions were approximated as closely 
as possible, and not only was the chemical action noted, but 
physical changes were studied also. 

For the purpose, however, of corroborating the analytical 
data obtained during the large-scale tests, a series of parallel 
tests were made in the laboratory on small samples of stock. 



DEPILATION 75 

The material used in these laboratory tests was shaved free 
from hair at the start so that this factor of uncertainty might 
be eliminated. 

The first series of large-scale tests was for the purpose of 
determining the effect of various quantities of lime on the 
stock as well as the influence of the time of treatment. Both 
fresh and bettered (strengthened) limes were employed. Sev- 
eral packs of skins were treated with 5 per cent of lime, and 
at the end of two days showed an increase in weight of about 
40 per cent above the trimmed weight. The lime absorbed was 
about 1.30 per cent. Several packs were then run with 10 
per cent of lime, and gave an increase of 50 per cent from the 
trimmed to the second day out of lime, with an absorption of 
3.65 per cent of calcium oxide. One lot treated with 10 per 
cent of lime gave an increase of 61 per cent, with an absorp- 
tion of 3.09 per cent of calcium oxide. These results seem to 
indicate that the larger amount of lime produces a greater 
increase in weight and causes a greater absorption. 

An experiment was made to see if one portion of lime would 
completely depilate a pack of hides. For this test 10 per cent 
of lime was added to the stock in the paddle, and without 
changing was allowed to remain in the same liquor for 10 
days. At the end of this time the hair was only partly loos- 
ened, it requiring immersion in warm water and considerable 
work in beaming before the hair was completely removed. 
Thus an excess of lime was always present, but for some rea- 
son the changes which had taken place greatly retarded the 
depilating effect. An interesting point in connection with this 
pack was that after 8 days the lime in the solution increased 
again, showing that it was being drawn from the hides. 

In conducting the analytical work, the loss of hide sub- 
stance was always observed. In all cases where the lime was 
applied fresh the loss was greater than when the lime was 
strengthened. This would seem to indicate that new lime 
has a greater solvent action upon what is called hide substance 
than an old lime. May it not be possible that in the old limes 
a protective colloid is formed? To illustrate this point: if a 



76 PRACTICAL TANNING 

pack was treated with fresh lime, run for a day, the lime dis- 
carded, a fresh lime made up, and so on for a number of days, 
the loss of hide substance was much greater than where the 
stock had been strengthened with the same amount of lime. 
In the pack cited abcve — being treated for 10 days — it was in- 
teresting to note that the amount of dissolved hide substance 
increased slightly from that found after the second day. From 
the appearance of the resulting leather, however, there can be 
no doubt that some action had taken place which had a de- 
cided influence upon the character of the product. 

The record of pack weights at different stages of liming 
showed, without exception, that the greatest weight occurred 
on the fourth day. This was due to the fact that up to that 
time the lime was being absorbed, but the action was not suf- 
ficiently great to cause the hair to drop off. The decrease fol- 
lowing the fourth day was on account of the loss of hair. This 
was shown fairly conclusively in the laboratory tests, where 
the hair had been eliminated before treatment, these showing 
no loss after the fourth day. It may be of interest to note 
a typical increase from samples that were freed from hair and 
depilated with 5 per cent of lime, which was made fresh each 
day, and from a series treated with 5 per cent of lime 
strengthened each day : 

Fresh, Strengthened, 

increase increase 

Days percent percent 

1 42.10 42.93 

2 2.60 2.10 

3 4.14 4.10 

4 1.30 1.41 

5 170 170 

6 0.30 3.60 

These results are of interest, as showing that about 80 per 
cent of the total increase in weight occurred during the first 
day. From this it might be assumed that the absorption of 
lime should give a similar condition. To show, however, what 
did happen to hides treated with fresh and bettered lime, the 
following results may be noted : 



DEPILATION 77 

Fresh Strengthened 

Ash Lime Ash Lime 

in ash in ash 

Original dry weight, per cent.... 0.66 33.67 0.51 32.80 

After 1 day 3.15 59.82 3.14 ' 56.61 

After 2 days 3.30 74.45 3.71 78.98 

After 3 days 4.25 76.58 4.19 80.49 

After 4 days 4.52 78.46 4.50 90.64 

After 5 days 4.21 86.69 4.81 86.07 

After 6 days 5.18 82.69 4.67 84.23 

The large-scale tests agreed with these laboratory experi- 
ments, showing that most of the lime was taken up during 
the first two days ; and both show that the absorption of lime 
is not wholly responsible for the increase of weight. In other 
words, the absorption of lime and water do not bear any def- 
inite relation to each other. The higher ash in the fresh lime- 
treated stock would seem to indicate that the fresh lime has 
a greater solvent action on hide substance than the bettered 
lime treatment. This is shown by the fact that the ash is 
higher in the former case, while the lime in the ash is less. 
This would again indicate that possibly used lime may have 
a protective colloid effect. 

It is generally assumed that during the liming process fat in 
the hide is saponified, thereby producing a lime soap, and that 
the formation of this soap tends to open the fibers. That this 
saponification is not complete is shown by the following re- 
sults : 

Fat on dry weight 

Fat Fresh Strengthened 

lime lime 

Original, per cent 5.1 1 5.21 

After 1 day 1.86 2.77 

After 2 days 2.05 1.96 

After 3 days 1.24 1.96 

After 4 days 3.01 4.43 

After 5 days 1.22 1.05 

After 6 days 1.25 2.88 

Although these results are not very concordant, they do 
show that practically all of the fat which is saponified be- 
comes so in the first 24 hours. This would perhaps account 
for the increase in weight of the stock during the same period. 
It seems fairly safe to say that 75 per cent of the fat was 
saponified during the first day, and after that practically no 



78 PRACTICAL,, TANNING 

more saponification took place. This is closely related to in- 
crease in weight, when it is remembered that practically 80 
per cent of the increase in weight took place during the first 
day. 

Many tests were run in the laboratory as well as on a work- 
ing scale to determine the loss of hide substance occurring in 
the lime liquors, and the following examples will illustrate 
what was observed : 

Hide substance lost, per cent 

Fresh Bettered 

Days lime lime 

1 0.51 0.S5 

2.. 0.253 0.39 

3 0.43 0.59 

4 0.66 0.64 

5 0.24 0.17 

6 0.25 0.34 

These data are of interest from the fact that if we add the 
first column we will have a loss of hide substance amounting 
to 2.143 per cent and if the second column is added it would 
give about the same result. As a matter of fact, the second 
series of tests are for solutions that had not been changed, and 
indicate the amount of hide substance which had dissolved dur- 
ing the time the stock was in the solution. In the first series 
the solution was made up fresh each day ; and in the second se- 
ries the same solution was used continuously, new lime being 
added to the old solution. These results need some explanation : 
Do they show again that after a lime has been used for one day 
some change has taken place which protects the so-called hide 
substance ? It may be possible that the hide substance that has 
been dissolved changes rapidly into some form which does not 
respond to the tests applied for hide substance. Similar re- 
sults have been noted in the working tests, although in these 
instances a somewhat larger amount of hide substance was ob- 
served. The question now arises : What is understood by 
hide substance? It is fairly well agreed that hide substance 
does not necessarily mean gelatin, but rather the albuminous 
material present as connective tissue between the fibers and 
the layer between the epidermis and true skin. 



DEPILATION 



79 



From the observations noted above it seems fairly safe 
to assume that the proper manner to apply a straight lime 
solution would be to put the stock into a lime liquor which is 
only a few days old at most, and then work up through the 
series to a fresh lime liquor. The lime that has been used 
thus for the new pack should then be discarded. This does 
not mean, of course, that a hard and 
fast rule can be made which will 
work for all classes of stock, but it 
is to be interpreted as being general 
procedure. 

Lime is the most common agent 
for de-hairing, although it also has 
disadvantages. In preparing the so- 
lution, a quantity of fresh lime is 
slaked by placing it in a shallow 
tank similar to that used by build- 
ers, and adding sufficient water to 
moisten it thoroughly. At the end 
of one or two hours it becomes 
heated and falls to a powder. Suffi- 
cient water is added to form a thick 
paste which may be kept for several weeks or even months 
without much change. When required for use, a suitable 
quantity is dug out, stirred with water to remove rocks, and 
then run into the pits. It is necessary to provide a surplus of 
solid lime to replace that taken up by the hide. It is impossible 
to set any fast rule as to the proper quantity of lime, but a 
safe margin is 10 lb. for each 100 lb. of hide. 

The usual method of liming is to place the hides one at a 
time into solution, taking care that each hide is well immersed 
before entering the next one. The hides are taken out 
("hauled") each day, the liquor bettered and well "plunged up" 
with a lime plunger ( figure 42) in order to distribute the un- 
dissolved lime throughout the pit. They are then thrown back 
("set"Y, care being taken to spread them out fully. In some 
yards the hides are joined by hooks ("toggled") and reeled 




Figure 42. — Lime plunger. 



80 PRACTICAL TANNING 

from one pit to another, or to the same pit. Sometimes hides 
are suspended in the liquor, and the limes are kept in motion 
by means of a paddle, or by blowing in air. The most corn- 




Figure 43. — Beam knife. 

mon means, however, of agitating the liquor is by the ordinary 
paddle-box run at intervals during the day. 

The action of lime on the hide is to swell up and soften the 
epidermis cells, dissolve the mucous layer, and loosen the hair 
so that on scraping with a blunt knife (figure 43), or work- 




Figure 44. — Whitney model "S" unhairing machine 



ing on the machine (figure 44), both the epidermis and hair 
are easily removed. The action on the true skin is very vigor- 
ous, causing the hide to become plump and swollen, at the 
same time dissolving the cementing material of the fibers, thus 
causing them to become split up into finer fibrils. This swell- 
ing is probably due to hydrolysis of the albuminous matter 



DEPILATION 



81 



and to formation of a lime soap. Not only does the liming 
process remove the hair and epidermis, but it is also of value 
in the re-fleshing process, as it gives the hide a greater firmness, 
very desirable when working with the knife (figures 45, 46, 
47), or on the machine (figure 48). The time of liming varies 
with the season of the year and with the kind of stock treated ; 
it may run from 3 to 60 days. The age of the lime greatly in- 
fluences the time of treatment as well as the character of the 




Figure 45. — Broad flesher. 



Figure 46. — Spring style fleshing knife. 




Figure 47. — Monitor flesher. 

finished product. Old limes de-hair much quicker than fresh 
ones. It is often customary to place the hides in an old lime 
for several days, or until the hair and epidermis have started 
to loosen, then change them to a fresh lime which produces 
the desired plumping of the fibers. Great care, however, must 
be taken that the limes do not become too old, especially in 
hot weather, as this condition will very likely produce a trans- 
parent swelling of the tissue, with destruction of hide 
substance. 

The period of liming has a marked influence on the finished 
product. Short liming produces a tight grain, while long lim- 
ing produces a loose, open grain. The former condition is 



82 



PRACTICAL TANNING 



necessary in the production of shoe leather, while the latter 
effect is desirable in glove and fancy leathers. 

Sodium sulphide. — This material is largely employed as a 
depilating agent. It may be used alone or in conjunction with 
other substances if desired. When used alone it has the prop- 
erty of rapidly and completely dissolving the hair, but causes 
the stock to plump excessively, with the production of a false 
grain and loss of measurement. It has its advantages as a 




Figure 48. — Automatic roller fleshing machine. 



time-saver, produces more weight, and a tight grain. The 
strength of the sodium sulphide solution commonly used is 20° 
bk. (barkometer) at a temperature of 75 Q F. The stock is 
then placed in this liquor, run for 2 hours, allowed to rest over 
night, run for half an hour, washed, neutralized with sodium 
bicarbonate, and then again thoroughly washed. 

For some classes of leather the sodium sulphide is made into 
a paste or a heavy liquor and applied to the flesh side. Skins 
so treated are piled-down over night, and on the following day 
the hair may be readily removed by hand. This method is 



DEPILATION 83 

the one commonly employed by wool-pullers and by tanners 
of other grades of stock carrying valuable hair. 

Sodium sulphide mixed with lime materially helps in the 
removal of fine hairs. For this purpose, about 20 per cent of 
sulphide on the weight of the lime is sufficient. The sulphide 
should be added to the lime before slaking. For hydrated 
lime and sulphide mixture the two should be boiled together. 
Whenever sodium sulphide is used in conjunction with lime 
it should be at the start of the de-hairing process. Many tan- 
ners, however, use the sulphide after the stock has been limed 
for several days, but this would seem to be poor policy if its 
addition is for the purpose of removing fine hairs. This con- 
clusion is based on the fact that sodium sulphide has no sol- 
vent action upon hair which has once been treated with lime, 
no matter how strong the sulphide solution may be made. 
On the other hand, clean hair will dissolve rapidly even in 
dilute solutions of sodium sulphide. A good system, and one 
which has been found to give satisfactory results, is to use a 
series of three of four pits, adding the sodium sulphide re- 
quired to the oldest liquor when the new stock enters, the 
head pit being straight lime liquor. No loss of hair occurs by 
this treatment, although the stock is free from fine hair and 
has the appearance of limed stock, except that it has a better 
grain than is obtained with either sulphide or a long lime 
treatment. 

To determine the effect of the lime and sodium sulphide 
mixture, several working tests were made with a 5 to 1 com- 
bination. The gain in weight from the soaked to the first day 
out of the liquor was 43.24 per cent; during the second day 
the gain was 2.45 per cent; while after the third day there 
was a loss of 0.55 per cent. The loss was caused by the com- 
plete slipping of the hair. The amount of lime absorbed in- 
creased from day to day, but no more sulphide was taken up 
after the second day. The laboratory tests conducted along 
the same lines did not agree very closely with the working 
tests, owing to the previous removal of hair. Analysis of the 
hide samples, however, gave results which may show that there 



84 PRACTICAL TANNING 

is a reason why lime stock is not so tight-grained as stock 
treated with sodium sulphide. For example, note the fol- 
lowing : 

New 1 day 2 days 3 days 

Percentage of fat 3.55 1.19 1.57 2.11 

Percentage of ash 0.67 2.35 2.71 3.07 

Percentage of lime in ash.. 31.60 68.20 69.10 75.92 

These records show that the percentage of fat remaining 
after the treatment was about the same as noted for lime stock. 
The absorption of lime was somewhat greater after the first 
day than was observed for straight lime treatment, but on the 
third day it had increased to that of limed stock. It can be 
fairly safely assumed that the lime would continue to be ab- 
sorbed if a longer treatment had been given. 

In the working tests with straight sodium sulphide solution, 
the gain in weight after one day was considerably less than 
with any of the previous treatments, being about 16.25 per 
cent. This was due of course to the solvent action of the sul- 
phide on the hair. One pack was treated for four days with 
the sulphide, but showed little gain after the first day. The 
hair-free laboratory samples, however, showed a gain of more 
than 50 per cent after the first day. Analyses of the hide gave 
6.70 per cent of fat when new 'and 1.90 per cent after one 
day, and 0.44 per cent of ash when new and 0.94 per cent 
after one day. 

It might be expected that stronger alkali would saponify 
the fat more completely, but the data obtained do not seem to 
bear this out. Analyses of the liquor showed that the stock 
at the end of 24 hours had absorbed 0.126 per cent of sodium 
sulphide and 0.124 per cent of sodium hydroxide (caustic 
soda). 

Among several other methods of depilating which were 
studied, the one in which a mixture of sodium sulphide and 
calcium chloride were used should be mentioned. The ad- 
vantages of this treatment were found to be in the freedom 
from false grain, complete removal of hair, saving of time, 
and better measurement than straight sodium sulphide. The 
method consisted in running the stock in a 20° bk. sulphide 



DEPILATION 85 

solution, to which had been added one- fourth as much calcium 
chloride as sulphide. 

Sodium sulphide is produced on a commercial scale by 
fusing together a mixture of sodium sulphate and carbon, the 
reaction being essentially as follows: 

Na 2 S0 4 +2C = Na 2 S+C0 2 

The mass is lixiviated with water and concentrated to crys- 
tallization. The product thus obtained is sold to the trade 
as "crystal sulphide." By carrying the evaporation to the dry 
state, a solid is obtained which is practically free from water 
of crystallization, and is known in the trade as "double 
strength." 

Sodium sulphide is also a by-product from the manufac- 
ture of other chemicals, barytes, for example. 

When used in depilation, sodium sulphide ionizes into two 
compounds as follows : 

Na 2 S-f-H 2 = NaHS+NaOH 

Arsenic sulphide. — When the red sulphide of arsenic 
(AS2S2) is mixed with hot water and added to lime, or mixed 
with quicklime during slaking, it increases the depilating ef- 
ficiency of lime. It is especially good for fine leather to which 
it gives the necessary stretch, softness, and clearness of grain, 
without the loss of hide substance, and the loosening effect 
caused by ordinary liming. The amount used varies some- 
what, but may be said to run from 0.1 to 0.4 per cent of 
realgar (arsenic sulphide) and 4 to 6 per cent of lime, reck- 
oned on the weight of the green skins. 

Caustic soda. — This chemical is produced by the electroly- 
sis of sodium chloride, or common salt. By passing an elec- 
tric current through a concentrated solution of salt, the water, 
in decomposing, gives the hydroxyl ion to the sodium and 
the hydrogen ion to the chlorine, thus : 

+ _ + _ + _ +_ 

Na Ci + H O H > Na OH + H CI 

Owing to the fact that the hydrochloric acid is also broken 



86 PRACTICAL TANNING 

up by the current, a further decomposition takes place, re- 
sulting in the generation of chlorine gas. The final products 
of electrolysis, therefore, are sodium hydroxide or caustic 
soda, chlorine, and hydrogen. 

When dissolved in water to the amount of 1 lb. per gallon, 
caustic soda forms a solution which is known as above normal, 
in which strength it will dissolve the hair very rapidly, but 
will not plump the stock. By using such a strength, skins or 
hides may be depilated in the course of half an hour. Such 
strong solutions are of no interest in practical tanning, as 
they are difficult to handle and very expensive. A small quan- 
tity of caustic soda, however, added to lime, has a decided ad- 
vantage, as it aids materially in plumping the stock and short- 
ens the time of treatment, and is spoken of as "sharpening the 
limes." 

Calcium sulphydrate. — This compound -is a powerful de- 
pilatory, but is little used on account of its unstable character. 
It is probably formed to some extent when sodium sulphide or 
arsenic sulphide is added to lime. It may be produced by pass- 
ing hydrogen sulphide (a gas) into milk of lime until the 
latter becomes saturated. This is the substance largely sold 
as a patent depilatory for removing superfluous growth of 
hair. 

Arazym. — It has recently been discovered by Dr. Otto 
Rohm that hides and skins can be de-haired and bated in one 
operation by means of "tryptase" in an alkaline solution. This 
process gives especially good results on goat skins, and as no 
bating is necessary, the process is meeting with approval, al- 
though rather slow in adoption. 

Unhairing.* — When the process of depilation is complete, 
the skins or hides are removed from the pits and allowed to 
drain for half an hour or more. They are then placed on the 
beam, and the hair is removed by means of a blunt knife. 
Various machines have been devised to remove hair, and these 

* Both "unhairing" and "de-hairing" are used in this book, the former 
when referring to the mechanical operation, and the latter to the chemical 
process or the removal of hair in general. 



DEPILATION 87 

have been brought to such perfection that hand work has been 
almost entirely eliminated. The unhairing machine as shown 
in figure 44 represents a common type. It is similar in con- 
struction to the fleshing machine, but is provided with a blunt 
knife which works against the grain of the stock. 

Methods of depilation. — Having discussed the various ma- 
terials employed for depilation in a general way, let us con- 
sider a few methods which are claimed to give satisfactory 
results : 

Liming hides for upper leather. — 1. Green-salted hides 
that are intended for soft, supple leather — chrome or vege- 
table tanned — worked through a liming process according to 
the following directions, will be found to be sufficiently limed 
for de-hairing in six days. Exact quantities of lime and so- 
dium sulphide should be used, namely, 8 lb. of the former and 
2 lb. of the latter for every 100 lb. of hides. 

To start the liming process, slake 1^ lb. of lime for each 
100 lb. of stock, add it to the water in the vat, and plunge 
up well. Reel the chain of hides into the prepared lime, tak- 
ing care that each side is spread out flat and not rolled, folded, 
or twisted. After the hides have been 24 hours in this lime, 
reel them into the second lime, made by adding the same quan- 
tity of lime to water that was used in the first lime. Leave the 
hides in this lime 24 hours. Then make up the third lime the 
same as the second, and allow the hides to remain in it 24 
hours. Reel them into the fourth lime, which should also con- 
tain the same quantity of lime, and leave them in it 24 hours. 
The fifth lime should contain 1 lb. of lime, and the hides 
should remain therein 24 hours, when they are reeled into the 
sixth lime, which should contain 1 lb. of lime and 2 lb. of 
sodium sulphide. This lime should be warmed to 75° F., and 
the hides left in it 24 hours, when they are reeled into warm 
water and de-haired after two or three hours. The positions 
of the hides should be changed every day, and fresh lime used 
every day, the hides remaining in each lime 24 hours. 

After the hides have been de-haired, wash them with run- 
ning water for 15 minutes; then place them in water at 90° 



88 PRACTICAL TANNING 

F., and work them over the beam or on the machine, and then 
put them into the bating liquor. This process produces very- 
uniform leather. The hair should come off easily and clean. 
De-hairing out of new- lime gives hard, plump hides, a 
desirable condition for chrome tannage and for splitting out of 
lime. After de-hairing, the hides can be split, or they may 
be bated and pickled and then split; or bated, pickled, and 
tanned, and split after they are tanned. 

Although 8 lb. of lime will de-hair 100 lb. of hides, softer 
leather is obtained by using 10 lb. in 6 limes, starting with H 
lb., and using 2 lb. each day until the hides reach the fifth 
lime, which should contain 2\ lb. of lime and 1 lb. of sodium 
sulphide. Either of these processes produces satisfactory re- 
sults for chrome or vegetable tanning. If the hides are to be 
split out of lime, they should be de-haired, put into warm 
water, and worked by hand over the beam or on the machine, 
and left in cold water over night to harden for splitting. 

2. Sides that are intended for shoe leather and other soft 
and supple stock may be limed and de-haired with excellent 
results, according to the following instructions : 

By calling the pits A, B, and C, and numbering the packs, 
the method of procedure may be readily understood. The 
quantities of lime and sodium sulphide are based on 100 lb. of 
wet, fleshed hides. The temperature of the limes should be 
maintained at 70° F. The process is as follows : 

First day: Pack No. 1 is put into pit A, containing 5 per 
cent lime and 1 per cent sodium sulphide. 

Second day: Pack No. 1 is transferred to pit B, contain- 
ing 5 per cent lime and 1 per cent sodium sulphide ; pack No. 
2 is put into pit A, once used. 

Third day: Pack No. 1 is put into pit C, containing 5 per 
cent lime and 1 per cent sodium sulphide; pack No. 2 is trans- 
ferred to liquor B, once used ; pack No. 3 enters pit A, twice 
used. 

Fourth day: Pack No. 1 is removed; pack No. 3 is drawn 
from A, and new liquor consisting of 5 per cent lime and 1 
per cent sodium sulphide is made up with that pit; pack No. 



DEPILATION 89 

2 is transferred to A; pack No. 3 is put into C, once used; 
pack No. 4 enters pit B, twice used. 

Fifth day: Pack No. 2 is removed; pack No. 4 is drawn 
from B, and a new liquor is prepared as above; pack No. 3 
is transferred to B; pack No. 4 is transferred to A, once used; 
pack No. 5 is put into C, twice used. 

Sixth day: Pack No. 3 is removed; pack No. 5 is drawn 
from C, and new liquor prepared; pack No. 4 is transferred 
to C ; pack No. 5 is put into B, once used ; pack No. 6 is trans- 
ferred to A, used twice. 

When once started, this cycle can be kept up, and it entails 
only a small amount of handling of the stock. This method 
gives a good grain and full feel. On removing the hides from 
the lime liquor they should be thrown into water at 85° F. 
for a half-hour, then unhaired on the machine or over the 
beam. The next process is bating. 

Sodium sulphide process for dry hides. — : The immersion 
of hides in a solution of sodium sulphide removes the hair 
quickly, freshens the grain and imparts great toughness to the 
leather. This is an excellent process for heavy chrome 
leather for winter and work shoes. The hides should be split 
into sides, fleshed, and put into cold water over night. 

The de-hairing solution is prepared in the following man- 
ner: Put 200 lb. of sodium sulphide into a barrel two-thirds 
full of water. Turn on steam, and boil slowly until the sul- 
phide is dissolved. Let the solution stand until the foreign 
matter has settled and the liquor is cold, which requires 12 
hours, or over night. Only the clear solution should be used. 

Put enough water into a vat to cover the sides, and add 
enough sodium sulphide to make a 6 or 7° bk. liquor. The 
exact strength, however, is immaterial ; the stronger the liquor 
the sooner the hair is dissolved; but a good rule to follow is to 
start with a liquor of 6°, which requires about three days to 
accomplish the desired result. Put the sides, opened out well, 
into the liquor, and let them remain 24 hours ; then haul them 
out. Plunge the liquor up and put the sides back, for another 
24 hours ; then haul them out again. Plunge the liquor again, 



90 PRACTICAL TANNING 

and return the sides for another 24 hours. At the end of the 
third day the hair should have been reduced to a slimy mass, 
which can be easily washed off, leaving the hides clean. Put 
the hides into a wash-wheel with running water and wash 
them clean. If there is any hair that does not come off, the 
sides should be worked on a beam; and if this does not re- 
move the hair, add some fresh sodium sulphide solution to the 
liquor, and put the hides. back into it for another 24 hours. 
After washing, the hides are limed. 

Slake \ bushel of lime for each 100 sides in the pack, and 
add the slaked lime to water in a pit, put the de-haired hides 
into the liquor, and keep them therein two days, handling them 
each day. A little more lime may be used to make a softer 
leather. After the sides have been thus limed, wash them 
in cold water, and then split them into grains and splits, and 
bate and pickle them. 

This process destroys the hair, but makes plump and tough 
leather. Men who handle the hides through the sulphide 
process must wear rubber gloves to protect their hands from 
the caustic material. When hides are split out of the lime the 
grains are bated, pickled, and tanned; if they are split out of 
pickle or after tanning, they are bated and pickled whole. 
Opinions differ in regard to the best time for splitting. 

The condition of the flanks and the fineness of the grain 
depend largely upon how the grains are bated and de-limed. 

Notes on beam-house work. — In the process of liming 
hides for sole leather, and other kinds of firm and solid 
leather, much depends upon the condition of the lime liquors. 
A new lime has great swelling and plumping effect upon the 
hides. Such a lime, particularly if caustic soda is added to 
it, is strongly antiseptic. A short liming in new, sharp liquors 
is desirable in order that but little hide substance may be dis- 
solved. The plumping effect of such a lime is considerable, 
while an old lime liquor has a more solvent effect and does 
not plump the hides so well. Caustic soda in the lime liquor 
assists in getting the full plumping effect, but it must be used 
carefully or it will cause rough grain. 



DEPILATION 91 

Where sodium sulphide is used in the lime liquors, the de- 
hairing is hastened and the plumping effect of the lime in- 
creased; but unless the sulphide is used rather sparingly, the 
grain is liable to be coarse. An old lime liquor containing 
considerable sulphide makes leather more pliable than a clear, 
fresh lime liquor. An old lime dissolves hide substance, 
which means pliable leather, but the swelling effect of such a 
lime is less than that of a new lime. For sole leather, there- 
fore, liming should be done in new liquors to get the full 
plumping effect and to avoid the loss of hide substance. 

If pliability is an essential in the leather, the best procedure 
is to place the hides first in an old lime to get the softening 
effect, and then place them in a fresh lime where they will be 
plumped. The more mellow the lime liquors are the greater 
the flexibility of the leather. 

For some leathers, such as harness, fairly fresh limes con- 
taining sodium sulphide should be used. Such limes accom- 
plish the swelling and de-hairing rapidly, but do not dissolve 
enough substance to make the requisite degree of flexibility; 
and it is therefore advantageous to accomplish the latter effect 
in the bates. Bacterial bates dissolve considerable substance, 
and where pliability is desired, such bates should be used, es- 
pecially when liming has been done in fresh limes. 

Soft leather is obtained by somewhat long treatment in mel- 
low limes, followed by thorough bating and rather heavy 
pickling. This is the usual process for certain grades of up- 
per shoe leather, glove leather, etc. For leather that is to be 
finished dull, sodium sulphide is preferable in the limes ; and 
for that to be given a fine, glazed finish, red arsenic is best. 

Arsenic sulphide. — Where sodium sulphide is used in the 
presence of lime, the chemical reaction produces caustic soda 
and calcium polysulphide. Being soluble, this caustic soda has 
a pronounced action in the liming operation. Where arsenic 
sulphide is used in the limes, the reaction produces calcium 
polysulphide and insoluble hydrate of arsenic, and conse- 
quently differs from the results obtained with sodium sulphide 
to the extent that the caustic soda may influence the operation. 



92 PRACTICAL TANNING 

Arsenical limes have a characteristic action, due to the cal- 
cium sulphydrate which forms when red arsenic* is added to 
slaking lime. Sodium sulphide should be dissolved separately 
and added to the lime, but red arsenic should be mixed with 
the dry lime and slaked with it, or else added to the lime 
while it is slaking. Lime should, in every case, be thoroughly 
slaked and stirred before it is used. Unslaked lumps should 
never be allowed to pass into the lime liquor, as they are likely 
to burn the hides. Caustic soda may be added direct to the 
lime liquor. Its use can be recommended for heavy leather, 
as it sharpens the lime, but not for light, soft, leather, the lat- 
ter being benefited most by the use of sodium sulphide or red 
arsenic. Caustic soda is useful in swelling and plumping the 
hides quite rapidly, but it does not assist in making soft 
leather. There is considerable bacterial activity in an old 
and mellow lime, and such a liquor, on account of its solvent 
effect, tends to produce a leather that is soft and loose, and 
has a dull grain. Hides that have been passed through such 
a lime should therefore be put into a fresh lime to be properly 
swollen and plumped. 

Sun-dried hides should be de-haired with sodium sulphide 
in the limes, since such a process swells the fibers and freshens 
up the withered grain more than does lime alone or lime and 
red arsenic. De-hairing in a strong solution of sodium sul- 
phide and then liming for a few days is another excellent 
process for dried hides. Soaking in a sulphide soak, supple- 
mented by working in a dry mill, is usually found to be the 
most satisfactory process which can be used on dry hides for 
upper harness, and sole leather. 

Liming for thin grain. — Leather can be made with a thick 
or a thin grain by certain manipulations in the beam-house. 
Hides can be so treated that when they are tanned they have 
a thick, solid grain, this being usually done by using sodium 
sulphide and de-hairing the hides rapidly. On the other 
hand by treating in only clean, white lime, the grain can 
be made soft and flexible, and so thin that when the 
leather is split after it is tanned the grains have consid- 



DEPILATION 



93 



erable substance and strength, even when the hides are split 
unusually thin. 

By shaving the hides green, liming them for 8 days, bating 
them until they are soft and low, and stirring them easily in 




Figure 49. — Unhairing on the Leidgen machine. 

the tan liquors, a thin grain is obtained. One process ac- 
complishing this is carried out as follows : 

The hides are first soaked 24 hours in clean water ; they 
are then fleshed and re-soaked 12 hours longer, drained, and 
passed into the first lime. This lime is prepared by using 
1 lb. of lime in sufficient water for 100 lb. of hides. The 
hides remain in this lime 24 hours, and are then hauled out 
and the lime is strengthened by adding another pound of lime. 
The hides are put back for 24 hours longer, then hauled out 
and put into the second pit. The third lime liquor should 
contain 2 lb. of fresh slaked lime for each 100 lb. of hides in 
the pack. At the. end of 24 hours the hides should be hauled 
out and placed in the third lime, prepared the same way as the 



V-h 



PRACTICAL TANNING 



second lime. Twenty- four hours later the hides should go 
into the fourth lime, which should be a little stronger in lime 
than the preceding liquor. At the end of 8 or 9 days the 
hides should be in condition to be de-haired. After they have 




Figure 50. — Hand fleshing on the beam. 

been de-haired, put them .into water warmed to 85° F. for 
6 or 7 hours ; then work them over the beam by hand, and get 
them as clean as possible. 

Liming for sole leather. — In liming this grade of stock, 
the hides are first treated with a mixture of 10 per cent of 
hydrated lime and 2 per cent of sodium sulphide, and left 
in the liquor for one day. On the second day they are trans- 
ferred to another paddle or pit containing 10 per cent of hy- 
drated lime and 1 per cent of sodium sulphide. On the third 
day, the hides are changed to straight lime liquor containing 
10 per cent of the weight of the stock. On the fourth and 
fifth days they are also changed to straight lime. On the 
sixth day they are thrown into the warm pool for half an 



DEPILATION 



95 



hour, after which they are ready for de-hairing. On removal 
from the warm pool, the sides are placed on a table, spotted 
for white hair, and then unhaired on the machine, (figure 49). 
Following the unhairing on the machine, the hides are re- 




Figure 51. — Inspection for fine hairs. 

fleshed on the machine and then hand fleshed on the beam, 
(figure 50). They are then inspected for fine hairs as shown 
in figure 51. 

Sulphide process for sides, kips, or calf. — The well- 
soaked and washed stock is put into a paddle containing a 
20° bk. solution of sodium sulphide at 70° F. The paddle 
is run for about 2 hours, when the wheel is stopped, and after 
that run for 5 minutes each hour. The stock is kept in the 
liquor over night, and turned from time to time during the 
morning. At about noon, the plug is drawn and the spent 
liquor let out. The paddle is filled with water and run for 
half an hour. One per cent of sodium bicarbonate is now 
added, and the wheel is turned for one hour. Fresh water is 



96 PRACTICAL TANNING 

next turned on, and the stock is washed for 3 hours. By this 
time it should be fairly free from sulphide and in a fallen 
condition. It is then removed from the paddle, and may be 
bated and pickled as desired. 

Sodium sulphide and calcium chloride on sides and kips. — 
Put into the paddle a weighed amount of sodium sulphide suf- 
ficient to make a 20° bk. solution. To this solution add one- 
fourth as much calcium chloride as sodium sulphide used. 
Raise the temperature of the solution to about 80° F., and 
then introduce the stock and run at intervals during the day. 
Allow the stock to remain in the liquor over night, and at the 
end of 24 hours wash thoroughly in running water for 1 hour. 
The stock is then neutralized with 2 per cent of sodium bisul- 
phite, running 1 hour in the liquor. The hides or skins are 
then thoroughly washed in running water, and are ready for 
the bate. 

Liming of calfskins. — After calfskins have been soaked 
and fleshed, they are put through the lime process. For light 
skins, liming according to the following directions will be 
found satisfactory in every respect, the skins being brought 
into condition for de-hairing in 4 or 5 days. For each 100 
lb. of skins 5 lb. of lime is used. It is thoroughly slaked and 
added to the water in the paddle, and 1 lb. of sodium sulphide, 
dissolved in hot water, is added. The temperature of the 
liquor is then raised to 75° F. ; the skins are thrown in, and 
the paddle is run at intervals during the day. The next morn- 
ing, 5 lb. of lime and 1 lb. of sodium sulphide are poured into 
the liquor; and the skins, which have previously been hauled 
out, are put back and left in the liquor with occasional stirring 
1 or 2 days longer, when the liquor is again strengthened in 
the same manner as before and warmed to 75° F., this tem- 
perature being maintained during the entire process. At the 
end of 4 days, the skins should de-hair easily, but it does no 
harm to leave them in the lime a day longer. Heavy skins 
require another addition of sodium sulphide and lime, and 2 
days more or longer in the liquor. The hair should come off 
easily without straining the grain. When taken out of the 



DEPILATION 97 

lime liquor, the skins should be thrown into water at 85° F. 
for a half-hour, then de-haired carefully, washed and put into 
the bate. 

Another satisfactory process of liming calfskins is carried 
out as follows : the quantities of lime and sodium sulphide 
being for 100 lb. of skins. The first solution contains 2 lb. of 
lime, and the skins are left in for 24 hours. The second so- 
lution contains 2 lb. of lime and 1 lb. of sodium sulphide, the 
skins also remaining therein 24 hours. The next day they 
are hauled out, the liquor is thoroughly plunged, and the skins 
are put back for 24 hours. The third lime is made up of the 
same quantity of lime and sodium sulphide as the second 
lime, and the skins are left therein 24 hours. The fourth lime 
contains 2 lb. of lime, and is warmed to 80° F. The skins 
remain in this for 24 hours, and then are put into clean water 
at 85° F. After having been in this water for 2 or 3 hours, 
they are de-haired. 

Lime and arsenic. — In this liming process, lime and 
red arsenic are used, and the skins are brought into good 
condition for chrome or vegetable tanning. To start with, 
use a new solution made by adding 2 lb. of lime, well slaked, 
to the requisite volume of water in the paddle. Leave the 
skins in this lime 24 hours. On the second day, haul them 
out, plunge the liquor, and put the skins back. On the third 
day, add 2 lb. of lime, stirring the goods at intervals during 
the day. On the fourth day, haul the skins out, and after 
plunging the lime, put them back. On the fifth day, add 3 lb. 
of lime, well slaked, and 1| lb. of red arsenic, slaked with the 
lime. On the sixth day, simply haul the skins out and put 
them back, plunging the liquor well. On the seventh day, add 
3 lb. of lime and 1| lb. of red arsenic, and warm the liquor 
with steam to 75° F. On the eighth day, haul the skins out 
of the lime, warm the liquor as before, and put the skins 
back. The hair should come off easily on the ninth day. 
After the hair has been removed, the skins should be washed 
in warm water, re-fleshed, and all the fine hair worked out. 
They are then washed and bated. 



98 PRACTICAL TANNING 

Red arsenic keeps the grain smooth and the skins flat; it 
also produces fine grain on the leather which takes a fine 
glazed finish. The lime and red arsenic should be mixed to- 
gether dry and slaked with hot water. Place the limed skins 
in warm water containing 12 oz. of borax to 100 gallons of 
water to soften the grain and dissolve the lime on the surface, 
so that the fine hairs and waste matter will come out readily 
when the skins are worked. The quantities of lime and ar- 
senic in the foregoing process are for 100 lb. of skins. 

The use of a paste of lime and red arsenic is not customary 
among tanners of calfskins; yet such a method of de- 
hairing, followed by liming for a few days, gives smooth, 
soft skins with fine grain and texture. The paste of lime 
and red arsenic should be prepared a day or two before using. 
Mix 50 lb. of lime and 2 lb. of the arsenic, and slake together 
with hot water. The mixture should be stirred while it is 
slaking, and enough water added to make it as thick as paint. 
The skins are spread out on the floor or a table, and the pre- 
pared mixture is spread upon the flesh side with a brush, the 
skins folded down the middle lengthwise, and placed in piles 
in a vat. When the vat is about three-quarters full, some 
boards loaded with stones are placed on the skins, and the 
vat is filled with water. After 5 or 6 days the skins are taken 
out of the vat, washed, and de-haired. Some skins require 
from 6 to 8 days before they can be de-haired. The next 
process is liming. 

For each 100 lb. of skins in the lot, use 14 lb. of lime and. 
5 lb. of red arsenic ; 1 or 2 lb. more of lime and a little more 
arsenic may be used for soft leather. The skins are limed 
from 3 to 7 days, according to their thickness, being stirred 
by the paddles 3 to 4 hours each day. Having been thus 
limed, the skins are next washed and bated. 

The following method of liming with lime and sodium sul-. 
phide, described under side leathers, produces good grain and 
full feel without much loss of skin substance, so it is a good 
process to use in preparing calfskins, kips, etc., for chrome tan- 
nage. When once started, the movement described entails 



DEPILATION 99 

only a small amount of handling of the stock. Calfskins 
having a heavy neck are split on the checking machine shown 
in figure 52. 

Liming of goatskins. — After softening, as shown in figure 




Figure 52. — Checking machine, used for splitting necks on 
calfskins. 

53, a liming process in which sodium sulphide is used, pro- 
duces first-class results and does not make fine-hairing neces- 
sary, is carried out as follows: 

For 100 lb. of skins, 3 lb. of lime and If lb. of sodium 
sulphide are used as a first lime, the skins remaining in it one 
day. They are then hauled out and the same quantities of 
lime and sodium sulphide are added. On the third day the 
skins are hauled out, and put back after the lime has been 
plunged. On the fourth day the lime is strengthened and 
warmed to 80° F. ; the skins are put back until the sixth day, 
when they are de-haired, washed, and bated. If they do not 
de-hair easily, the liquor should be warmed and the skins left 
in a day or two longer. 

Liming with lime and red arsenic produces fine-grained 



100 



PRACTICAL TANNING 



leather. To start with, the goods are put into a weak liquor, 
containing 2 per cent of lime, calculated on the weight of 
the raw stock. After being in this for a day they are hauled 
out and put back. On the third day, 2 per cent more of lime, 




Figure 53. — A typical beam-house of a goatskin tannery. 

well slaked, should be given. On the fourth day the skins are 
hauled out, the liquor is plunged, and the goods are put back. 
To strengthen the lime on the fifth day, 3 per cent of lime 
and 2 per cent of red arsenic, slaked together, should be added ; 
and on the sixth day the goods are hauled out and put back, 
so that those that were on top before are now on the bottom, 
and those previously at the bottom are on top. On the seventh 
day 3 per cent of lime and 2 per cent of red arsenic are added. 
On the eighth day it is advisable to haul the skins out and 
warm the liquor to 80° F., then put the goods back, and 
after leaving them one day longer de-hair them. They are next 
washed 10 minutes in cold water, re-fleshed, worked for fine 
hairs, and then bated. The exact quantity of lime to use and 
the number of days to leave the goods in the lime depends 



DEPILATION 101 

upon their thickness, heavy goods requiring longer liming 
than light, thin ones. For the preparation of glazed kid, a 
fairly long liming is required, usually 12 to 15 days. Either 
lime and arsenic or lime and sulphide may be employed. After 
the goods have been de-haired, they are re-fleshed, and passed 
into the bating process. 

Combination process. — Run 700 gallons of water into a 
paddle, and add 100 lb. of sodium sulphide crystals dissolved 
in hot water. Put a pack of skins into this liquor, and leave 
them until the hair is dissolved, when they are ready to be 
limed. The liquor swells the skins and dissolves the hair. 
The next process is liming. Slake 100 lb. of lime, and add 
700 gallons of water. Put the de-haired skins into this liquor, 
and turn them in it 2 or 3 days, then wash them and scrape 
the flesh side again. Some of the hairs which may be broken 
on the grain should be removed from the flesh side, and much 
of the remaining grease will come out at the same time. The 
skins are then in condition to be bated. 

Depilatory compounds for wool skins and hairskins. — 
The present methods of removing wool from. sheepskins and 
the hair from goatskins and other light skins are considerably 
different from the old-time process of sweating and liming, 
the latter having been replaced by the method of painting 
mixtures on the flesh side, of which lime is mainly the base. 
These usually contain lime and some sulphide, such as sodium 
sulphide or arsenic sulphide (red arsenic). By mixing lime 
with either of these substances, and adding water, a paste is 
obtained which, when applied to the flesh side of the skins, 
causes the hair or the wool to be loosened in a few hours. 
Methods of mixing lime and sulphides vary. It is usually 
considered good practice either to slake the lime with a solu- 
tion of sodium sulphide, or mix the lime with the sulphide 
first, and then slake with water; or in the case of arsenic sul- 
phide and lime, to place the two in alternate layers and then 
slake. The high temperature caused by the slaking of the 
lime produces a reaction between the sulphide and the lime, 
so that hair-removing compounds are formed 



102 PRACTICAL TANNING 

As a type of method, the following, which has been rec- 
ommended by the Light Leather Trades Federation of Great 
Britain, may be given (7-J lb. of sodium sulphide crystals to 
every 40 lb. of dry lime, are the desired proportions for all 
skins) : 

Take the 40 lb. of lime, slake in 9 gallons of water, and 
allow to stand for three days, so that all the hard substances 
are well slaked. Pass the slaked lime through a sieve with 
10 meshes to the lineal inch. Dissolve the 7^ lb. of sodium 
sulphide in 1 gallon of water, and add the sulphide solution 
to the lime, mixing well. The mixture is then ready for 
painting the skins, which should be pulled not later than the 
next day. As they are pulled they should be washed in clean 
water before they are put into weak lime. 

A suitable depilatory paint for all classes of skins is pre- 
pared as follows: 60 lb. of unslaked lime, 25 lb. of sodium 
sulphide, and 20 gallons of water. A wooden tub should be 
used for slaking and mixing. A thin layer of the unslaked 
lime is then placed on the bottom of the tub, and on this a 
thin layer of sodium sulphide crystals, followed by another 
layer of lime. The two ingredients are thus placed in alter- 
nate layers until all has been placed in the tub. The necessary 
amount of water to effect thorough slaking is now added a 
little at a time (about 10 gallons of water will be. sufficient). 
After slaking, the mixture should be left over night, the re- 
maining 10 gallons of water are then added, and the mixture 
is thoroughly stirred. Before being applied to the skins, it 
is better to pass the mixture through a fine sieve to remove 
any small lumps of unslaked lime, stones, etc. 

For the finer grades of leather, such as lambskins and goat- 
skins for glazed and glove leathers, upon which fine grain is 
essential, the use of paint composed of lime and red arsenic 
is preferred. It is better to mix the arsenic sulphide and the 
lime before slaking, so that the heat produced by the slaking 
of the lime produces calcium sulphydrate. 

M. C. Lamb has given the following method: "The arsenic sulphide 
is mixed with the unslaked lime in a suitable receptacle, in alternate 



DEPILATION 103 

layers of lime and arsenic, and the amount of water necessary to effect 
the slaking is then poured a little at a time over the mixture. Suitable 
quantities to use are 120 lb. of lime, 30 lb. of red arsenic, and 60 gallons 
of water. After the slaking has been performed, the mixture should be 
thoroughly mixed with a wooden spade, and diluted to the required 
consistence by the addition of 45 to 50 gallons of water. The paint should 
be allowed to stand over night before using, and may with advantage be 
passed through a fine sieve before being applied to the skins. When 
properly prepared, the paint should be pale green in color. Any trace 
of red or pink color is evidence that the mixture is not satisfactory, and 
that the necessary chemical reaction during the slaking process has not 
been satisfactorily effected." 

Depilating glove leather. — The modern glove-leather 
manufacturer has to deal with all kinds of skins, but chiefly 
with goatskins and sheepskins. Owing to the scarcity of raw 
skins, he is not able to choose as much as he formerly did. 
Cape sheepskins form the glove-leather dresser's main supply, 
and these are now in general demand by tanners and leather 
dressers for a great variety of purposes, including boot and 
shoe uppers and bag work. The following information rela- 
tive to glove-leather dressing is taken from an article in "The 
Leather Trades Review" : 

For painting fifty dozen average skins, 6 bushels of lime and 45 lb. of 
red arsenic are required. In preparing this mixture, care must be taken 
to get a perfect reaction between the lime and arsenic. This is best 
obtained by first thoroughly mixing the two together and breaking the 
lime into small lumps. The mixture should then be carefully and thor- 
oughly slaked with water and made into a paste-like mixture which can 
be painted on the skins in the usual manner. 

The skins are spread out on the floor or on a table, and the mixture 
is applied with a mop to the flesh side. As each skin is painted, it is 
folded over, flesh to flesh, and placed in a pile and left until the next day. 
When the painting is done in the afternoon, the skins are ready for 
pulling the next morning. The wool is generally sorted into four grades. 
The next process is liming, and the duration of this process varies, 
according to the skins under treatment, from 7 days to 2 or 3 weeks. The 
old one-pit method still obtains in many tanneries and is carried out as 
follows : The pit is started with 5 bushels of lime, and the pelts remain 
in the same for 2 days when they are withdrawn, and the liquor is 
strengthened by the addition of 2 bushels of lime. In this liquor the 
skins are left for a week, then withdrawn and a final addition of 3 bushels 
of lime is made to the liquor. The goods remain 1 or 2 veeks longer, 
as they may require. 

The amount of lime given above is sufficient for 50 to 60 dozen Cape 
sheepskins, but much latitude must be allowed, as so much depends upon 
local conditions, the season of the year and the condition of the goods. 
^During liming, the skins are drawn several times, and when the process 
is completed, they are drained and allowed to soak in clean water for a 
day or two. The addition of a pail or two of lime to the water is 
recommended. When the liming is completed, the skins are trimmed and 
fleshed, and left in water containing a little lime, after which they are 



104 PRACTICAL TANNING 

passed through water to which some lactic acid has been added to accom- 
plish a slight de-liming. 

Patented depilatories. — In addition to sodium sulphide 
used for the purpose of removing hair and wool from hides 
and skins and preparing them for tanning, patented depila- 
tories are obtainable, largely made from the same chemical, 
which have many points to recommend them, being very satis- 
factory for both wool-pullers and tanners to use; and the 
leather which is made from skins treated with them is char- 
acterized by toughness, pliability, and fine grain. These de- 
pilatories are used in various ways according to the kind of 
skin being treated and the qualities desired in the finished 
leather. 

Depilatory paints. — Following are several more prescrip- 
tions for making the paint : 

Put 25 lb. of lime into a tub, and add just enough hot 
water to cover it. Stir the lime until it is entirely slaked, 
and add more water as it is needed. In another tub or barrel 
dissolve 25 lb. of sodium sulphide in 10 gallons of hot water. 
Mix the lime and the solution of sulphide together, and allow 
the mixture to become cold before applying it to the skins. 

A suitable paint is prepared as follows: Mix 60 lb. of lime, 
30 lb. of sodium sulphide and 20 gallons of. water. Place 
a thin layer of the lime upon the bottom of a clean tub or 
vat, sprinkle on this a thin layer of the sulphide, and spread 
the remainder of the lime and sulphide in alternate layers. Ten 
or twelve gallons of hot water are next added, a little at a 
time, the mixture is thoroughly slaked, and is then left over 
night. The remainder of the water should be added, and 
then stirred up to a paint-like consistence. It is always ad- 
visable to pass a depilatory paint through a fine sieve to re- 
move particles of unslaked lime, small stones, etc. Hydrated 
lime is better than lump lime, and if the former is used, the 
proportions should be 60 lb., 40 lb. of sodium sulphide, and 
20 gallons of hot water. 

A good depilatory is made by dissolving sodium sulphide in 
hot water until the solution stands at 18 or 20° Be (Baume) 



DEPILATION 105 

test, and then adding 18 gallons of slaked lime. Apply this 
mixture to the skins when it is cold. 

A mixture of lime and red arsenic can be recommended 
for loosening the wool on skins for glove or glazed leather, 
since it makes fine, smooth grain. The proportions are 100 
lb. of lime and 25 lb. of arsenic, the two being thoroughly- 
mixed together dry, and then slaked with 50 gallons of hot 
water, and passed through a fine sieve. 

Applying the depilatory paint. — Spread the skins, one at 
a time, upon a table and apply the prepared paint upon the 
flesh side; then fold the skin with the wool on the outside, 
and place in piles until the next day, when the wool can be 
easily removed. Only enough of the mixture should be used 
to saturate the skin and cover it evenly, and none should be 
allowed to run off" into the wool. Rubber gloves should be worn 
to protect the hands during this work. 

When the weather is cold, 6 or 7 skins may be placed in 
a pile ; but during warm weather not more than 3 or 4 should 
be so placed, and if they are to be left for 24 hours or longer, 
they should be singled out and each pelt should lie by itself. 
7 The wool becomes loosened in a few hours, but it is best if it 
is not removed until the next day. Very young lambskins, 
however, should be "pulled" as soon as the wool is loosened, 
and then put into cold water to which some sodium sulphide 
has been added. They may be kept in this water for some 
time without injury, although it is advisable to pass them 
promptly into the lime. 

Liming after removal of the wool. — To start the liming 
of the skins, use 20 lb. of hydrated lime with 6 gallons of 
water for 100 average skins. Put the lime into water in a 
vat; put the skins in and leave them 1 day; then haul them 
out, and add 10 lb. of lime with 5 gallons of water, and put 
the skins in for another da} 71 , then haul them, add 7\ lb. of 
lime, and return for another 2 days. 

Liming for Mocha and castor gloves. — In the depilation 
of skins for Mocha, castor, buff, and chamois leather, it is nec-\ 
essary to employ a long liming, which in some cases is pro- \ 



106 PRACTICAL TANNING 

longed to 30 or 40 days. For this treatment strong limes 
are also used, and a certain amount or arsenic sulphide is 
usually added. The outer grain is then removed on a beam 
with a round stick, the operation being known as frizzing. 

Method of using arazym on goatskins. — Soaking: It 
is very important that the skins be thoroughly milled and 
soaked, and it is advisable to soak them for one day more than 
is considered sufficient for the lime or sulphide processes. See 
that the heads and necks are carefully worked out, that is, 
freed from grease and flesh. 

First day. — Make up the following solution for each 100 lb. 
of skins, dry weight in hair: 

Light weight Heavy weight 
skins skins 

Water, gallons 125 125 

Caustic soda (76 per cent), pounds... 3i 4 

Temperature, degrees F 80 to 82 83 to 85 

Time to remain in caustic solution, hrs. 36 48 

Heavy hard-natured skins may stay in the liquor for 60 hours. 

Run the skins in the paddle one hour when first put in, and 
then for 10 minutes each, in the evening before closing down 
and in the morning when starting up. 

When the skins are to remain in the caustic solution over 
Saturday and Sunday, put them into liquor late on Friday, 
and reduce temperature 5° (according to the nature of the 
skins). 

The pack that has to stay in the caustic solution on Sunday 
and Monday is put into the solution as late as possible on 
Saturday, with a drop in temperature of about 8° (according 
to nature of skins). 

Third day. — Run off the caustic solution, and put the skins 
into a solution consisting of 10 lb. of bicarbonate of soda and 
125 gallons of water for 100 lb. of skins, dry weight in hair. 
The temperature after the skins are in is 80 to 84° F. 

Run for one hour, then add, according to the nature of the 
skins, for lights, 12 oz. of arazym, and for heavies, 16 
oz. of arazym, per 100 lb. of skins, dry weight in hair. Run 



DEPILATION 107 

for 20 minutes more, then leave in solution until the follow- 
ing morning. 

When skins are to remain in the de-hairing bath over Sun- 
day, drop the temperature 10°, and reduce the arazym 30 per 
cent, which means 8 oz. for light skins, and 12 oz. for heavy 
skins. 

Fourth day. — Take the skins out and unhair. It is im- 
portant that the skins from the unhairing machine be put 
into tepid water (about 65° F.) at once. They should not 
be left in dry condition either in a box or on a pile for 
any length of time. Wash in tepid water for 10 minutes, 
then flesh. If after fleshing the skins do not go into the 
bate at once, put them into tepid water. Weigh skins and 
then bate with "oropon A special" as follows (it is very im- 
portant that the quantities of water and skins are in the right 
proportion, and for each 100 lb. of skins there should be 400 
lb. of water). 

First liquor. — The skins are washed in the old bating liquor • 
used for the previous pack over night at a temperature of 85° 
F. for light skins, and 90° for heavy skins. The time of bating 
is 10 minutes (paddle 5 minutes). If no old oropon liquor is 
available for the first pack, substitute a solution of 4 oz. of 
oropon per 100 lb. of skins. 

Second liquor. — In the second bating liquor the skins are 
bated over night. The quantity of oropon required is 16 oz. 
per 100 lb. for heavy skins, and 12 oz. for that quantity of 
light skins. The temperature should be 90° for heavy and 
85° for light skins. Paddle 5 minutes. 

The oropon necessary for the first pack is fermented in 
five times its weight of water for 24 to 48 hours at 110° F. 
(24 hours in summer, 48 hours in winter). From the sec- 
ond pack on, that is when for the preliminary bate an old over- 
night bating liquor is available, it is not necessary any more 
to ferment the oropon, but it is simply added to the fresh 
bating liquor before the skins go in. 

After the skins are in the bating liquor, make certain it 
is on the alkaline side, that is, you should get a fair reaction 



108 



PRACTICAL TANNING 



with phenolphthalein, and if not, add £ per cent of soda ash 
on the weight of the skins. 

When bating over Sunday, either put the skins into the 
bating liquor on Saturday afternoon, without the preliminary 
washing in the old bating liquor, reducing the temperature 
about 5° and the quantity of oropon about 25 per cent; or 
do the bating on Sunday in the usual manner, taking care, 




Figure 54. — Fleshing. 

however, that the skins, over Saturday and Sunday, are left 
in water made strongly alkaline by the addition of a solution 
of saturated lime water. 

Fifth day. — Take skins out, slate, wash for 5 minutes in 
tepid water in paddle, and tan as usual. 

For the swelling and de-hairing liquors it is advisable to 
take into one paddle a comparatively small quantity of skins 
with a large volume of water — about 125 gallons for 100 lb. 
of skins in the hair, dry — because in these liquors the skins 
are considerably swollen. After the skins are de-haired, 
washed, and fleshed (figure 54), they do not take more room 



DEPILATION 109 

than in the ordinary bating process, and the quantity of water 
(50 gallons per 100 lb. of skins, bating weight) is sufficient. 
For the swelling and de-hairing liquors, take 3 reels for a 
quantity of skins for which in the regular bating process you 
would take one reel. For instance, if the regular bating packs 
consist of 900 lb. of skins, divide this quantity for the swell- 
ing and de-hairing liquor into 3 paddles each containing 300 
lb. ; however, for bating in the oropon special put them all into 
one paddle again. 

The finished leather is improved by giving a somewhat 
heavier bottoming with vegetable tan in the dyeing, so as to 
fill it up. Care should also be taken to dry slowly at mod- 
erate temperature. 



CHAPTER IV 

DE-LIMING, DRENCHING, BATING, PUERING AND 
PICKLING 

It is essential that the lime or other depilating agent should 
be completely removed after it has done its work, since its 
action on tanning is very injurious. Its presence has a ten- 
dency to weaken the fiber or produce a harsh-feeling grain. 
For sole and belting leather it is only necessary to de-lime the 
stock, and for soft leather this de-liming should not only be 
complete, but the stock should be brought to a flaccid and open 
condition. Ordinary de-liming may be accomplished by weak 
organic acids or certain chemicals, while bating, puering, and 
drenching, all of which tend to produce soft leather, must be 
brought about through fermentative, bacterial or enzyme ac- 
tion. Pickling consists in treating the de-limed, bated, puered 
or drenched stock with a combination of salt and acid, usually 
sulphuric. Drenching, which consists of a fermenting in- 
fusion of bran, sometimes follows bating or puering, but it is 
often resorted to independently of the other treatment. 

The two terms "bating" and "puering" formerly meant 
two distinct processes, the former being applied where 
pigeon or hen manure was used, and the latter where dog 
manure was employed to remove the lime and open up the 
stock. Today, however, bating is most commonly used, and 
puering only in connection with the conversion of goatskins 
into leather. 

De-liming. — Where de-liming only is desired, this may 
be accomplished by purely chemical means. Lime, being of 
an alkaline nature, adheres tenaciously to the hide fiber, and 
so cannot be readily removed by washing in plain water. 
An excess of strong acid must be avoided on account of its 
swelling effect upon the pelt, with subsequent damage dur- 
ing the tanning operation. What is especially required is 
that the de-liming agent should form an easily soluble com- 

110 



DE-LIMING, DRENCHING, BATING, ETC. Ill 

pound with the lime. An excess of the reagent must not 
have an injurious action on the pelt, and it must be obtainable 
at low cost. 

Test for de-liming. — A simple test to ascertain whether 
skins are sufficiently bated and de-limed is to touch a cut 
edge of the skin with phenolphthalein solution. If there is 
lime still present, a violet coloration is produced, but when 
the skin is entirely de-limed, there is no such coloration. 

Sulphuric acid. — By exercising great care this acid may 
be used as a de-liming agent for stock that is to be tanned 
in acid hemlock liquors. The stock should be run in a much 
diluted, slightly warm solution, until the lime is nearly neu- 
tralized; it is then thrown into clear water to finish the de- 
liming. 

Hydrochloric acid. — This mineral acid is somewhat safer 
than sulphuric, but must be perfectly free from even a trace 
of iron, and the paddle should have no iron surface exposed. 

Sulphurous acid. — The most satisfactory mineral acid is 
sulphurous. It may be generated as a gas by burning sulphur 
in a stove, and allowing the sulphur dioxide (SO2) to be 
absorbed in water. An excess of this acid is not harmful 
to the stock, and leaves it in a somewhat plump condition. 

Sodium bisulphate. — Ordinary nitric-cake may be used in 
place of sulphuric acid. This material is a by-product from 
the manufacture of sulphuric acid, in which sodium nitrate 
is treated with sulphuric acid to furnish the necessary amount 
of nitric oxide required during the process Care must, there- 
fore, be taken to guard against the presence of any nitric 
acid in the product. 

Boracic acid. — This may be used to advantage as a sur- 
face de-liming agent on sole leather, the amount required 
being about 2 per cent on the weight of the stock. Experi- 
ence has shown that the treatment should be carried out in 
a paddle, otherwise patches will appear giving irregular color 
to the finished leather. Among the various chemical de- 
liming agents and bates which may be used in preparing hides 
and skins for tanning, boracic acid is one of the most efficient 



112 PRACTICAL TANNING 

for that purpose. The hides or skins are bated in the usual 
manner, and are then immersed in a drench of boracic acid, 
which removes the last trace of lime, and makes the grain soft 
and clean. When the acid is used alone for the purpose of 
de-liming it makes the grain soft and silky, hastens the tan- 
nage, and prevents the grain from becoming contracted in the 
tan liquor. Light skins for chrome and vegetable tanning 
are sometimes given a drenching with boracic acid after they 
have been bated, a paddle being used during the operation. 
When soft, silky, leather is required, it is advisable first to 
use a commercial bacterial bate, such as oropon, and then 
drench with boracic acid, and pickle with formic acid and 
salt. Excellent results as regards grain, texture, and color 
are assured when skins are treated in this manner. 

Carbonic acid. — The use of carbonic acid has been sug- 
gested as a de-liming agent, in which case the carbon di- 
oxide gas (CO2) is allowed to bubble through the water in the 
paddle. The first action is to form the neutral carbonate, 
but as more carbon dioxide is introduced, the soluble bicar- 
bonate is produced and the stock consequently de-limed. 

Lactic acid. — In recent years this de-liming agent has come 
into general use. Lactic acid is formed when milk sours. On 
a commercial scale it is produced by adding the lactic ferment 
to a solution of glucose. It comes into the trade either in a 
30 or 60 per cent solution. When employed for de-liming, 
2 lb. should be used for each 100 gallons of water, at a tem- 
perature of about 90° F. Like other de-liming agents, the 
best results are obtained in the paddle. A slight excess of this 
acid produces considerable plumping, which is a decided ad- 
vantage in treating hides for sole leather or other heavy stock. 

For 800 to 1000 average limed sheepskins, 20 lb. of lactic 
acid and 20 lb. of salt are used. The water in the paddle 
should be warmed to 85° F. ; if it is cooler than this, more 
salt is required to keep down the plumpness. Half of the acid 
and all of the salt should be added to the water before the 
skins are put in, and the remainder of the acid after they have 
been in 15 minutes. The time required for drenching should 



DE-LIMING, DRENCHING, BATING, ETC. 113 

be about 45 minutes in a paddle; in a still vat or tub, 2 or 3 
hours, the skins being stirred two or three times during that 
time. Several packs of skins may be put through this drench, 
with a fresh addition of 15 lb. of lactic acid for each succeed- 
ing pack, adding 5 lb. at first, and 10 lb. after the skins have 
been in 15 minutes. When drenched, the skins should be 
rinsed in warm water and pickled. 

Lactic acid may be used for goatskins in the following man- 
ner: After the skins have been bated, prepare a bath in a 
paddle with warm water, and for 100 lb. of skins add -| lb. 
of lactic acid and an equal quantity of salt. The water should 
be at 90° F. before the skins are put in; they are paddled 20 
minutes, then rinsed and pickled. This method is advanta- 
geous for goods that are intended to be colored, as the acid 
cleanses them thoroughly. The process can also be carried 
out in a drum, in which case only a few minutes is re- 
quired to remove the last trace of lime from the skins. 

Formic acid. — This compound is prepared on a large scale 
by heating sodium formate with sulphuric acid. The result- 
ing acid comes to the tanner as a 60 per cent solution. It 
is very effective as a de-liming and plumping agent, and many 
tanners prefer it to lactic acid. It is used in the same pro- 
portions as given for lactic acid. 

Formic acid and lactic acid drench. — A mixture of 4 parts 
formic acid and 1 part lactic acid is efficient in drenching 
skins, less than -| pint of the mixture being sufficient for 100 
washed skins. The goods are paddled 30 minutes or longer 
in the drench at a temperature of 90° F., rinsed, and pickled. 
This drench may also be used after a regular bate. Drenched 
with formic acid, skins tan into clear-grained and uniformly 
colored leather. 

M. C. Lamb, of the Leathersellers' Technical College, Lon- 
don, describes a method of de-liming and pickling with formic 
acid, which he has used successfully, as follows : 

The goods, after washing free from surplus lime in the paddle water 
at 85° F. for 30 minutes, are ready for de-liming. The de-hming is best 
done in the paddle-wheel; the goods are placed in a vessel, together with 
sufficient water at 90° F.; paddling is commenced, and then the following 



114 PRACTICAL TANNING 

solution, previously prepared, is added: 2 lb. of formic acid (40 per cent), 
and 5 lb. of common salt, for each 100 lb. of limed skins. 

The goods are paddled until flaccid and fallen, which will generally 
require about 30 minutes, when they are removed and are ready for 
pickling. Pickling is best carried out in a drum, but it may also be done 
in a paddle. The proportions recommended are 10 lb. of formic acid, 20 
lb. of salt, and 20 gallons of water for 100 lb. of skins. 

Butyric acid. — This is another chemical product of recent 
introduction. It may be used in the pickling of calfskins 
for chrome or vegetable tanning, especially for the two-bath 
process, when it is used in the following manner: The skins 
are bated with any satisfactory bate or in a bran drench, 
and are then pickled in a drum with a solution of 10 lb. of 
salt, and 10 oz. of butyric acid in 15 gallons of water for 100 
lb. of skins. The skins are turned in this liquor for an hour; 
they are then given the first chrome process, which in this case 
is made of 4 to 6 lb. of sodium bichromate, 1 lb. of butyric 
acid, and sufficient water, say 15 gallons. This method of 
pickling and tanning is said to produce leather having a par- 
ticularly soft grain and agreeable feel. 

Ammonium chloride. — This material can be used to good 
advantage for dressing leather. It is a strong bating agent, 
converting the lime into calcium chloride, which is very soluble 
and easily removed. The ammonia generated, according to 
the Otto P. Amend process, may be neutralized with hydro- 
chloric acid, and the bath used continuously. The amount of 
ammonium chloride used at the start should be about 3 per 
cent of the weight of the stock, and 1 per cent is added to 
each subsequent pack. The temperature should be maintained 
at about 90° F. to get the best results. This method is es- 
pecially adapted to calf and side leather where a depleting 
action is not desired. 

The following process is said to be excellent for goatskins 
for chrome tanning: Dissolve 20 lb. of sal-ammoniac (am- 
monium chloride) and 70 lb. of salt in 700 gallons of water 
at 95° F., for 50 dozen skins. Paddle the skins in this liquor 
for two hours, then leave them in over night. Sal-ammoniac 
acts upon the goods like a bate or puer, having, however, the 
advantage that the workman can control this process while he 



DE-LIMING, DRENCHING, BATING, ETC. 115 

cannot always control the old-time puering. The next morn- 
ing the skins are transferred to the pickle in a paddle- 
wheel consisting of 10 lb. of formic acid and 8 lb. of salt, at a 
temperature of 85° F. After an hour in this liquor the skins 
are in condition to be tanned. This removes all the lime, and 
strengthens the fibers so they will stand the corrosive action 
of the chemicals and acids used in chrome tannage. 

Ammonium butyrate. — One of the newer chemical prod- 
ucts for de-liming and bating is made by neutralizing butyric 
acid with ammonia. It produces the best results as a bate 
when used upon skins that are to be put into the tanning 
liquors in a soft or neutral condition. The skins become per- 
fectly de-limed, white, and soft, and no injury results when 
an excess is used. It may be used alone or with any other 
bate. For bating calfskins it is used alone, the quantity rec- 
ommended being 1 to 1^ lb. for 100 lb. of skins. The am- 
monium butyrate is dissolved and added to warm water in the 
bating paddle. The goods are put in and paddled for a half- 
hour; then allowed to rest for 2 hours, and then paddled 
another half-hour, when they are taken out and either pickled 
or tanned. 

Sodium dichromate. — The value of this process lies in the 
employment of a chromium compound as a base, a solution of 
it forming the main ingredient of the bate. The liquor may be 
prepared as follows : 

Prepare a saturated solution of 2 oz. of sodium dichrom- 
ate in water, pour it into a vat containing 1,000 gallons of 
water, and stir thoroughly. This quantity is sufficient for 
20 to 40 hides, which are thrown into the prepared bate, and 
left therein for 24 hours, being stirred occasionally. The 
temperature of the bath should be about 80° F. The hides 
may be run in the liquor a short time, and then left in it over 
night or longer. They are then fine-haired, washed in warm 
water, and are ready to be tanned. About 2 oz. of dichromate 
are used for 2000 pounds of hides or skins, green-salted 
weight. The use of sodium dichromate as a bate has been 
patented by Henry Schlegel, of Lapeer, Michigan. 



116 PRACTICAL TANNING 

Sodium bisulphite. — This chemical has marked de-liming 
action, but on account of its acid character it does not pro- 
duce a true bating effect. For certain classes of leather, how- 
ever, it may be employed to advantage. 

Ammonium phosphate. — For sole leather the use of such, 
materials as ammonium phosphate and ammonium oxalate are 
said to have some value as de-liming agents. In using these 
salts an insoluble condition of the lime is produced which, 
remaining in the leather, helps to give it body. 

Zinc sulphate. — When limed hides are thrown into a solu- 
tion of zinc sulphate, a double decomposition takes place, 
which results in the formation of calcium sulphate and zinc 
oxide, both being insoluble in water. The hides are therefore 
filled and added body is secured. 

Coal-tar bates. — Several of the aromatic acids have been 
suggested as de-liming agents, some of which have been used 
with more or less success. Among these should be mentioned 
crude cresotonic acid, a mixture of phenol and cresols; oxy- 
naphthoic acid ; napthalene mono and disulphonic acid ; sali- 
cylic acid ; as well as phenol and cresol sulphonic acids. 

Several years ago the Martin Dennis Co., of Newark, N. J., 
put on the market a preparation known as "C. T. bate." This 
compound consisted of a mixture of sulphonic acids, and 
was used in a 1 per cent solution. All of these coal-tar bates 
are more effective as de-liming agents than as true bates or 
puers. 

Drenching. — By drenching is usually understood a method 
in which some form of fermentation is employed, the sim- 
plest of which consists of fermenting bran infusion. Not only 
is drenching employed to remove the lime and open up the 
stock, but it is often applied after bating or puering to bring 
the skin to a clean and acid condition. During fermentation, 
the principal products formed are lactic acid and acetic acid, 
together with some formic acid, butyric acid, hydrogen sul- 
phide, and amines. Drenching takes place most satisfactorily at 
a temperature of about 90° F., and is usually complete in from 
12 to 18 hours. Unless liquefying bacteria have been intro- 



DE-LIMING, DRENCHING, BATING, ETC. 117 

duced during the bating, no injury to the stock can result. 
The following suggestions may be . found useful : 

Method of de-liming {drenching) with bran. — Take a half 
barrel of bran, and add enough water to make it mushy; cover 
it up, and let stand in a warm place for 48 hours to sour. 
Into a vat large enough to treat 400 skins run the requisite 
volume of water and empty the sour bran into the same. Mix 
thoroughly, and heat to 90° F. Throw the pack of skins into 
the prepared drench, and treat them for 3 hours, heavy skins 
a little longer. The skins will be made soft and clean by this 
treatment, and, if intended for black leather, will require no 
working on the beam; but if for colored leather, it is advis- 




Figure 55. — Bate beam-stone. 

able to work them out on the beam so that the grain will be 
clear and clean. Washing in warm water after drenching puts 
the skins into the best condition for pickling and tanning. 

Other bran drench formulas. — Take 50 lb. of bran; add 
water to make a mush, and let it stand until sour; then put 
the sour bran into a paddle together with 700 gallons of warm 
water, and process the skins until they are soft and clean. 
Rinse them in warm water; work them over the beam with a 
bate beam-stone (figure 55), and then pickle them. If acid is 
needed, 25 lb. of 28 per cent acetic acid should be added 

A process of drenching which is especially recommended 
involves the use of bran and lactic acid in the following man- 
ner: Run water into a paddle-wheel and heat it to 120° F. 
Put two pails of dry bran into the warm water and let stand 
over night The next morning bring the temperature up to 
95° F. Take one pint of lactic acid for each 100 lb. of skins, 
and put about half of it into the bran liquor; throw the skins 
in, and while the paddle is running, add the remainder of the 



118 PRACTICAL TANNING 

acid. Run the paddle for 2 to 4 hours, according to the thick- 
ness of the skins and the amount of lime in them, then take 
them out and rinse in warm water. This washing should not 
be neglected, especially if the leather is to be colored. The 
skins, after they have been rinsed, are ready to be pickled. 
For the second pack of skins, lower the drench liquor down 
about 12 inches, and run in an equal quantity of water. Heat 
the liquor to 95° F. Do not use any more bran, but take a 
pint of lactic acid for every 100 lb. of skins to be treated, and 
proceed exactly as described for the first lot. Continue in 
this way for 6 days; then run off the liquor and make up a 
fresh drench with water, bran, and acid, and proceed in the 
manner described. This method of drenching makes the skins 
soft and clean, and in good condition for pickling and tanning, 
no matter what the tannage may be. 

The following also is a reliable bran drench : Take a half 
barrel of bran, add enough water to make it mushy, and let 
stand 48 hours to sour. When sour, empty it into a vat half 
filled with water. Add 6 pints of acetic acid and 3 pecks (45 
lb.) of common salt, and heat to 95° F. This quantity of 
bating material is sufficient for 300 to 400 skins. Throw the 
goods into the liquor, and paddle for 4 or 5 hours ; then wash 
them in warm water if for black leather, or work them over 
the beam and then wash them, if for colored leather. This 
process produces soft and clean skins which can be pickled and 
tanned by any tanning process. 

Mild fermented drench. — A mild fermentation of an acid 
has proved to be a most satisfactory bate and de-liming proc- 
ess for hides which are to be tanned into soft, supple leather 
by a chrome or a vegetable tannage. Excellent results as re- 
gards full flanks, good break, and fine, even grain are obtained 
by allowing grape sugar or common glucose to become sour, 
and using definite portions of the same in combination with 
lactic acid for each pack of hides or grains. 

The process is a simple one, and is easily carried out: Dis- 
solve 100 lb. of grape sugar or glucose in 35 gallons of hot 
water in a barrel. Add several quarts of sour milk, and allow 



DE-LIMING, DRENCHING, BATING, ETC. 119 

to stand for two or three days at a temperature between 95 
and 105° F., when fermentation should be completed. Pre- 
pare a paddle-wheel with water at a temperature of 95°, and 
put into it 2\ quarts of the sour sugar solution. For every 
100 lb. of stock to be bated take 1 pint of lactic acid, and put 
about half of it into the prepared bate in the paddle-wheel 
before putting in the hides, and when the latter are in, add the 
remainder of the acid. Three or four hours are usually suf- 
ficient to run the goods in the paddle-wheel. On being taken 
out, they should be thoroughly washed with water. The im- 
portance of this simple washing is too often overlooked, and 
its necessity cannot be over-emphasized if a good clear grain, 
which will color evenly, is desired. For the second pack of 
hides, the bate liquor is lowered about 12 inches in the paddle- 
wheel, and the loss made up with fresh water. The tempera- 
ture is brought up to 95° F., and 2\ quarts of the sour sugar 
solution and 1 pint of lactic acid is added for every 100 lb. of 
stock, as directed for the first pack. Continue in this way, 
running off a little of the liquor for each pack, for 6 days ; 
then run off all the liquor, retaining, however, about a barrel- 
ful with which to mellow the new liquor, which is prepared 
with fresh water. 

It should be pointed out that the amount of sugar solution 
used, namely, 2| quarts per pack, is based upon the volume 
of liquor in the paddle-wheel. The average capacity of a 
paddle-wheel is between 2000 and 2500 lb. of stock. The 
action of the sour sugar is, however, so mild, that a wide 
range in the weight of the stock bated with the given quantity 
of the sugar solution is permitted without danger. 

Puering and bating. — Under this head are included such 
materials as give the results desired through bacterial or en- 
zyme action. 

The process commonly called bating or puering frees the 
skins from lime and alkaline sulphides acquired during the 
process of liming, and makes them soft and clean and in the 
proper condition to be pickled and tanned. Hen and pigeon 
droppings and dog dung have been used for many years and 



120 PRACTICAL TANNING 

although these materials are unpleasant, they produce results 
difficult to obtain by the use of others, and many tanners con- 
tinue to use them. Goatskins are sometimes puered with a 
mixture of chicken droppings and dog dung, but the latter is 
also employed alone. 

To prepare the material, soak it in hot water for two or 
three days before using. Mash it well, stir it occasionally, 
and strain it through a wire strainer to get rid of pebbles, 
feathers, etc. ; this, however, is not always necessary. The 
skins should first be washed in warm water to remove sur- 
face lime, then be placed in a used bate liquor which has been 
warmed to 80° F., and left in the same for 12 hours. From 
such liquor they are placed in a fresh bate warmed to 85°, and 
paddled in the same for several hours, or until they are soft 
and silky. They are next fleshed, scudded, rinsed or drenched, 
and pickled or tanned. 

Bating with molasses. — Sour molasses makes an effective 
bate for hides for heavy leather. The molasses is soured by 
putting 7 gallons into a barrel of water, adding 1 gallon of 
milk to assist the souring, keeping the solution at 90° F., and 
stirring occasionally until sour. More than one barrel is 
required, so that more molasses can be souring while the first 
is being used. 

To use the sour molasses, fill a paddle-wheel with enough 
water to cover 50 sides, and add 8 pails of the sour molasses. 
The sides remain in the bate at least 30 minutes, and a longer 
bating will do no harm, although there is always danger of 
bating too low. Judgment must be used as to how long to 
continue the process. When the bate becomes weakened by 
the lime which works out of the hides, more sour molasses 
should be added, say 6 pails to 200 sides. If the paddle holds 
50 sides, put in 1^ pails of molasses after taking out each pack 
of hides, and keep the temperature of the bate at about 80° 
F. The bate should not be made fresh for each lot of hides, 
but molasses should be added to it. When the bating is over, 
withdraw the hides and rinse them in cold water in another 
paddle-wheel for a few minutes, and then put them onto sticks 



DE-LIMING, DRENCHING, BATING, ETC. 121 

for the tanning liquors. The bated hides will contain consider- 
able lime, but a few hours in the liquor will take it all out. 

Bating with glucose, sulphur, and yeast. — In working 
with this process, the skins are limed, unhaired, and washed. 
A bath at 95° F. is next prepared, consisting of 5 per cent 
glucose syrup and 1 per cent sulphur, computed on the weight 
of the skins, and about 1 lb. of yeast for every 1000 lb. treated. 
The bath prepared in this manner is allowed to stand 24 hours 
to become thoroughly fermented. At the end of this period 
the temperature of the liquor is raised to 100°, and the hides 
or skins are put into it. v 

In order to have a continuous bath, half the original quan- 
tity of sulphur, glucose, and yeast is added at the same time. 
In working this process, it is not necessary to keep the skins 
constantly in motion, but only stir them occasionally. Heavy 
hides will be free from lime and in soft and open condition 
at the end of 8 hours; lighter skins in a proportionately shorter 
period. 

On removing the pack, the temperature of the bath may 
be raised, and after adding half of the original quantity of 
sulphur, glucose, and yeast, another pack may be treated, thus 
making it possible to work two packs each day in the same 
vat. It will be understood that a continuous bath would in 
time become too concentrated from solutions of calcium com- 
pounds, and thus prevent or retard fermentation. This dif- 
ficulty is obviated by drawing off half of the solution every 
time after treatment of the second pack. 

The hides or skins show no trace of lime after treatment, 
and they are soft and open, and have a smooth, silky grain. 
As there is nothing in this bate to cause putrefaction, there is 
no loss of hide substance, and the skins, without further 
drenching, can go at once into the tan liquors. Where pick- 
ling is part of the process, the skins can be pickled at once 
and then tanned. This is the Oaks patented process of bating. 

By adding 2 per cent of ammonium chloride in the first 
bath, the efficiency of the bath can be improved. 

Dog dung. — Despite the unpleasantness of its use, dog dung 



122 PRACTICAL TANNING 

is an efficient bate for leather that requires a soft, fine, and 
silky grain. The material may be used alone or combined 
with the droppings of hens and pigeons. If dog manure is 
kept for some time, it becomes heated of itself, burns up, and 
becomes useless; consequently, it is placed in barrels, covered 
over with enough water to soften it, and allowed to ferment 
for two weeks, or until it has resolved itself into a pasty condi- 
tion. In this way it can be kept for months in covered bar- 
rels without losing any of its bating action. When it is to 
be used, it is stirred into boiling water (by this means a great 
many of the bacteria are killed, but not the spores) until, after 
decanting off several times, all of the soluble matter has been 
removed, and only the waste portion remains behind; but all 
sand must be allowed to settle again from the liquor, because 
if any is allowed to remain it is likely to injure the grain. 
This settling is best done in a large vat. 

For 100 pieces of calfskins or 50 sides it is customary to 
reckon about 10 to 12 quarts of dog durig, while for 30 dozen 
sheepskins about 50 lb. of the material are used ; and for 1000 
lambskins or goatskins, 100 lb. or more. The proper amount 
of the bate is placed in the paddle-wheel in water sufficient for 
the pack of skins to be treated. The temperature of the liquor 
at the beginning should be about 90° F. The skins should re- 
main in the bate for 2 to 3 hours, or at the longest, until the 
flesh remaining on them can be readily removed. It is injur- 
ious to the skins to bate them too long. 

After the process is completed it is well to rinse off the 
skins, and then place them at once on the beam or the flesh- 
ing machine. By placing them in fresh water, the flesh be- 
comes tender and is not removed as readily as when it is in 
the mellow condition in which it comes from the bate ; conse- 
quently, as little water as possible is used, so that the mellow- 
ness of the skins is not lost. 

In this process of bating it is easily possible for undesirable 
fermentation to take place and injure the skins. The duration 
of the bating in a normal case should occupy a definite time, 
regulated by the temperature, strength of the liquor, and tex- 



DE-LIMING, DRENCHING, BATING, ETC. 123 

ture of the skins, as well as by the degree of fermentation 
which the bate has developed. This method of bating is not 
patented. 

Hen manure. — For calfskins and side leather it is custom- 
ary to employ hen or pigeon manure in place of dog manure. 
The usual quantity used is a half bushel to 50 sides or 100 
skins. The manure is placed in a barrel with warm water and 
allowed to ferment for several days, when it is added to the 
paddle liquor. Manure bates may be used for some time with- 
out changing, but care must be exercised to prevent too violent 
an action, which may damage the stock, causing what is 
known as "bate runs " 

Dermiforma. — This is a prepared bacterial bate which has 
been introduced as a substitute for the old-time bates. The 
methods of using it described below, have proved satisfactory 
and the results desired have been obtained. 

It should be remembered that bacterial action is governed 
by different temperatures, and if it is desired to reduce or 
deplete the hides or skins, the temperature of the bating liquor 
should be kept close to 95° F. during the process. Experience 
has shown that a different grain is obtained at different tem- 
peratures; consequently, if the liquor is kept near this tempera- 
ture, the skins will be reduced more quickly and the grain will 
be finer. This applies to all classes of stock. 

The quantity of dermiforma to be used for every 100 lb. of 
skins varies. In the bating of goatskins, 4 lb. are used, and 
the same quantity in bating calfskins. Sheepskins, however, 
may be bated with 2 lb., and the same quantity bates hides and 
kips, while sealskins require 3 pounds. 

It usually requires about four hours to get calf, seal, and 
sheepskin in condition to be pickled or tanned. It requires 
good judgment to determine the exact time for the bating 
process ; consequently, no general rule can be laid down, as 
some tanners do not bate hides longer than two hours at 95°. 
If it is desired to plump the stock, H lb. of the bate will be 
sufficient for 100 lb., the time required being generally from 
2 to 4 hours, and in some cases where hides are being plumped 



124. PRACTICAL TANNING 

for sole leather, they may remain in the liquor over night. 
The temperature should be normal or not over 80° F. 

In using dermiforma in tanning liquors — either sweet or 
natural sour liquors — 1| lb. to every 100 lb. of green hides will 
plump them, and the leather will gain in weight. Where ex- 
tract liquors are used entirely, the result is better, and the tan- 
nage more rapid with the above proportions. In all cases, the 
hides must be thoroughly washed from the limes, or the pro- 
portions given will not suffice. More bate is required when 
an excess of free lime is carried into the bating process. 

Bating is done most advantageously in a vat with paddles, 
and not in a stationary tub, as the action of the paddles causes 
the liquor to be stirred, thus de-liming more quickly. A 
warm bate depletes or reduces the goods; a cold bate plumps 
them. When de-liming is completed, and the skins are soft 
and silky to the touch, they should be removed from the bath, 
rinsed in warm water, and then either pickled or tanned. 
Skins are bated most satisfactorily in warm liquor, while for 
hides for plump and heavy leather a cold bate is best. 

Dr.- Rohm's bate "oropon C" for regular packs. — 
Treatment of the skins before the bate is the same as usual. 
It is advisable to wash them thoroughly before the bate to 
free them as much as possible from lime. In the case of 
sulphide, neutralize as usual. For this bate the quantity of 
water and temperature are as usual, and the time of bating is 
2 to 4 hours for calfskins, and 4 to 6 hours for hides. The 
quantity of oropon is always calculated on the weight of the 
wet skin's and according to their nature thus : 

8 to 10 oz. per 100 lb. for calf and split grains, and 10 to 
12 oz. per 100 lb. for insplit hides (used for furniture, etc.) 

The liquor can be re-used, and in this case add, for the 
second and following packs, about half or even less of the 
oropon used for making fresh liquor. It is advisable to warm 
the old liquor over-night the first two days to accelerate fer- 
mentation. After the liquor has been used two days it will 
be noticed that fermentation grows stronger. To keep it in 



DE-LIMING, DRENCHING, BATING, ETC. 125 

control, run off each day about 6 to 12 inches of the liquor 
(more in summer than in winter). Before running off, stir 
the liquor well to get rid of as much dirt as possible. As a 
rule make up the bate fresh once every two weeks, but in 
doing so, leave about a fourth of the old liquor in the paddle. 
Bating process.— Always heat the water first, then put the 
oropon in undissolved. After stirring thoroughly put in the 
skins The further treatment is the same as usual. Watch 
the process closely to see how the skins fall, and do not take 
them out until they are as low as desired. In case they fall 
too quicklv, reduce the quantity of oropon proportionately the 
next time.' If they do not fall enough, add to the bate 0.1 to 
2 per cent of oropon (dissolved in a bucket of water and 
added while the skins are paddled), at the same time raise the 
temperature of the liquor in case it has cooled down too quick- 
ly If, after one hour, the skins are still too high, repeat this 
operation until a satisfactory result is obtained. The next 
time a correspondingly higher concentration is used. If over 
night bating is preferred, use about 20 per cent less oropon 
than indicated above, and a temperature of from 80 to 90° F. 
before skins are put in. 

Dr. Rohm's bate "oropon A B" for limed goatskins.— 
Use 30 gallons of water for each 100 lb. of skins, and the 
usual quantity for regular packs. 

Bating, first liquor.— -The skins are first washed in an old 
bating liquor. If no old oropon liquor is available, substitute 
a light solution of 4 to 6 oz. of oropon for each 100 lb. of 
skins or better, wash the skins in the used dog-manure liquor. 
Temperature.— For soft skins, 90 to 95° F. (before the 
skins are in) ; for hard skins, 95 to 105° F. (before the skins 
are in). 

Second liquor.— In this liquor the skins are bated over night 
(put in about four o'clock, paddled 10 to 15 minutes, and 
left until the next morning). In the morning they are paddled 
again for 15 minutes, and if low enough, are taken out. In 
preparing the bating liquor, always heat the water first, then 



126 PRACTICAL TANNING 

put in the oropon without previously dissolving it, and, finally 
put in the skins. 

Quantity of oropon for 100 lb. of skins. — For South Amer- 
icans, Brazils, etc., 8 to 10 oz. ; for Russians, 8 to 10 oz. ; for 
Chinese, 12 to 16 oz. ; for Mochas and Patnas, 14 to 16 oz. ; 
and for Northwesterns, 16 to 18 oz. 

Temperature. — 95 to 105° F. (before skins are in), accord- 
ing to the nature of the skins. 

In case the skins are not reduced enough, add more oro- 
pon, starting with about 20 per cent of the original quantity. 
If, after about an hour, the skins are still too high, repeat 
the operation until the skins are as low as desired. The next 
time, of course, correspondingly more oropon is used. In 
bating over night, fermentation will raise the skins to the 
surface of the water, which action is desirable. It is probable 
that the first two or three packs will not come up, as the 
fermentation is too weak at the start. It will strengthen grad- 
ually, however, and the fourth and following packs will rise 
over night. 

Martin Dennis' "puerine." — Take a clean 50-gallon barrel, 
remove the head, put in 25 gallons of water and heat to 130° 
F., then, while stirring vigorously, put in 100 lb. of puerine. 
Cover the barrel with an old burlap bag to assist in retaining 
the heat. After 24 and 48 hours, add 10 gallons of water at 
140° F., stirring well each time. At the end of 72 hours the 
puerine is ready for use. The barrel will be full, and each 
gallon taken therefrom will contain 2 lb. of puerine. When 
using the prepared puerine always stir thoroughly before tak- 
ing any from the barrel. 

First pack. — Have the desired quantity of water in the pad- 
dle, heat to 95°, put in stock, and then add, for every 1000 
lb. of stock, 12 lb. of puerine (6 gallons of the prepared 
puerine). 

Second pack. — Use 8 lb. of puerine (4 gallons of the pre- 
pared) for every 1000 lb. of stock. 

Third pack. — Use 6 lb. of puerine (3 gallons of the pre- 
pared) for every 1000 lb. of stock. 



DE-LIMING, DRENCHING, BATING, ETC. 127 

Fourth and all following packs. — Use 4 lb. of puerine (2 
gallons of the prepared) for every 1000 lb. of stock. 

Once a week allow the puer paddle to settle for four 
hours, then draw off from the top about a fifth of the bating 
liquor. This is easily done by having a plug on the the side of 
the pit at the proper distance from the top. Clean out the 
pit thoroughly every three months by drawing another plug 
from the bottom. 

It is impossible to explain here how long the stock should 
be bated, but it should be left in the bate until in the judgment 
of the operator, it is "low" enough. 

The puerine bating liquor improves with age, and it must 
not be expected that the first few packs will be as well bated 
as those which follow. In this respect it is the same as a 
manure bate. When the bating assumes a bluish, slate color, 
it is in prime condition. If, at any time, this puerine bating 
liquor suddenly becomes yellow, it is an indication that too 
little puerine is being used. 

Puerine D.- — The Martin Dennis Co. of Newark, N. J., has 
also on the market a bate which is used the same as oropon. 
This bate, as well as oropon, is made from dry pancreas com- 
bined with ammonium chloride and some inert material. Its 
action depends upon the presence of tryptase and to some ex- 
tent on lipase, the former acting as a solvent on the albumin- 
ous material, while the latter has the tendency to break up 
the fats. 

Pickling. — After the stock has been bated or puered it is 
necessary to drench or pickle it before tanning. Drenching is 
usual where the stock is to be vegetable tanned and pickling 
is employed where chrome tannage may follow. The sub- 
ject of drenching has been covered above, and the same 
methods as outlined may be applied after the bate. The fol- 
lowing suggestions will be found useful when pickling is 
desired : 

Sulphuric acid and salt. — To 40 gallons of water, add 40 
lb. of salt and 5 lb. of sulphuric acid ; this forms a stock pickle, 
12 gallons being used for 100 lb. of skins. The pickling is 



128 PRACTICAL TANNING 

accomplished most rapidly in a drum, the skins being run in 
the liquor at least 1-|- hours, then allowed to press and drain 
over horses for several hours or until the next day. 

Another formula calls for 2 lb. of sulphuric acid, 15 lb. 
of salt, and 15 gallons of water for 100 lb. of skins. The 
drum containing the skins is started, and after it has turned a 
few times, the solution of acid and salt is poured in and the 
drumming is continued from 15 to 30 minutes. Either of these 
processes produces good results, and there is no guesswork 
about the quantity of acid and salt to use, and therefore no 
uncertainty. 

Formic acid and salt. — The formula for this pickle is 10 
lb. of the acid, 20 lb. of salt, and 15 gallons of water for 100 
lb. of skins. The process is carried out in the same manner 
as with the sulphuric acid. An excellent way to pickle the 
skins, no matter which acid is used, is to put them into the 
drum together with three quarters of the water needed. The 
salt is dissolved in the remainder of the water, and the acid 
is added to it. The drum is started, and the acid and salt 
solution is poured in through the trunnion, and the drum al- 
lowed to run 30 minutes. 

Hydrochloric acid and calcium chloride. — In the manufac- 
ture of white chrome leather, a decided advantage in color 
may be obtained by using a pickle of calcium chloride and 
hydrochloric acid. To prepare this pickle, make up a solu- 
tion of calcium chloride by dissolving 40 lb. of the salt in 40 
gallons of water, and add 8 lb. of hydrochloric acid. To 
pickle, use 12 gallons for each 100 lb. of stock. 

Pressing grease from pickled sheepskins. — The follow- 
ing method of removing grease from pickled sheepskins has 
been found satisfactory in many cases: Get a sufficient num- 
ber of sheet-iron plates as large as the press (hydraulic) will 
take, about 1/16 inch thick. Place one dozen skins on each 
plate, and spread out flat with the bellies and shanks folded 
in so as to have each plate of the skins about the same size. 
Place the butt of one skin as evenly as possible over the other 
until the press is full. It will be seen that the pressure comes 



DE-LIMING, DRENCHING, BATING, ETC. 129 

directly on the parts of the skins that need it most. After the 
pressure has been applied and the- skins have been pressed, 
throw them into a drum, together with warm salt water, and 
drum them until they have come apart and are well opened 
out. They are then in condition to be tanned. 

It is advisable to plaee sawdust or bran between the layers 
of skins to keep them from slipping, and apply the pressure 
very slowly as the stock is easily damaged at this stage. 

Gargoyle de-greasing fluid. — This preparation is used for 
de-greasing pickled sheep, goat, dog, and other skins carry- 
ing a large percentage of animal fats. The following process 
produces satisfactory results when the pickled skins contain 
a minimum amount of moisture but no dry spots. If there 
are any dry spots they should be wet down when taken from 
the casks in the drained pickled condition, then proceed as 
follows : 

Weigh the skins, separate each bundle by picking them apart 
one by one, place them in a clean drum without any water or 
other materials, and mill them in that condition for 5 to 10 
minutes, or until they are opened up free from wrinkles and 
quite plump. Then for each 100 lb. of pickled stock, take 
from If to 2\ gallons of de-greasing fluid, and heat to 100° 
F. in a steam-jacket ed kettle or over an electric stove, or by 
similar means where it is possible to avoid introducing any 
moisture. Add the de-greasing fluid to the mill with the skins, 
and mill together for about 30 minutes. 

If the skins are entered in the evening and they are very 
heavy or greasy in the necks and backs, which will be the case 
if many bucks are among them, it is advantageous to let them 
lie in the drum over night, and then mill again in the morn- 
ing for about 15 minutes. Then add through the gudgeon of 
the drum sufficient (1 lb. to the gallon) salt solution at 100° 
F. to allow the skins to become wet ; although without sufficient 
solution to cause them to float. The process is most efficient 
where there is no excess of water at this stage. The pickled 
stock, put in a drum 4 feet high and 8 feet diameter, should 
not exceed 400 lb. In this condition the skins should mill 



130 PRACTICAL TANNING 

about 15 minutes, when there should be added through the 
gudgeon of the drum enough salt solution to float the skins 
freely. Next, pull the plugs or put on a slat door to flush 
out the salt solution and grease. Put on the tight door again, 
and slowly feed enough salt solution at a temperature of 
100° F. to float the skins; then again put on the slat door and 
flush out. The skins are now ready for tanning. 

During this operation, in addition to removing the animal 
grease, a good deal of the acid is extracted, thereby leaving 
the skins in the best possible condition for tanning. In this 
way the necessity of drawing pickle is eliminated, also the 
wringing and pressing of skins. 

De-greasing fluid. — This attacks the "sheep grease" con- 
tained in the skins, dissolving and diluting it, so bringing it 
into solution; and when washed with warm brine (salt water) 
the grease is all removed. Precaution must be taken that the 
temperature does not exceed 100° F., and that the pickled 
skins are kept in contact with the saturated brine while wash- 
ing, or they will bloat and be destroyed. 

By this process, which naturally makes a flat leather, there 
is no danger of breaking the grain or distending the fiber. The 
process is beneficial to the stock, whereas wringing or pressing 
is detrimental; and perfect results are secured in the single 
operation described. 

Recovered grease. — The solution of fats and brine, as it 
flows from the drum while washing, should be collected in 
wooden tubs or a large vat, then heated to boiling point and 
allowed to stand for 1 to 3 hours. The oil and fat will come 
to the surface, and the brine should then be drawn from the 
tank through a spigot or wooden faucet at the bottom of the 
vat until it has all been drawn from under the oil. Then 
more water should be run in with the oil ; boiled again to agi- 
tate it perfectly, allowed to settle the second time, and the 
water again drawn off. This operation should be repeated 
until all of the acid and salt have been washed from the oil, 
both of which are detrimental if the fats are to be used in the 
production of leather. Tests for acid should be made with 



DE-LIMING, DRENCHING, BATING, ETC. 131 

methyl-orange and tests for salt with silver nitrate. Natur- 
ally some Glauber's salt is produced, which is also eliminated 
by this process. Two washings should be sufficient. 

These recovered fats are valuable to the tanner, principally 
for making fat-liquors or emulsions. For sheepskins, it is 
recommended that one part of this recovered oil be added to 
two parts of "moellon degras" ; then add an equal quantity of 
water, and boil it until thoroughly incorporated. The recov- 




Figure 56. — Belt-knife splitting machine. 

ered fat may also be emulsified by the addition of soaps or 
alkalies, although excellent results have been produced by using 
it as suggested above. 

Splitting out of lime. — To make good chrome leather, 
hides should come from the unhairing machine firm and hard. 
If they are soft and flabby they will make poor leather, as 
there is nothing in chrome tanning that fills the hides or makes 
up for lost substance. After the hair has been removed, the 
sides should be washed in lukewarm water for 15 minutes and 
then worked over the beam for short hair. This work is im- 
portant, as all fine hair must be removed; and even if there are 
no fine hairs, working out the grain opens up the cells of the 
hides and makes the grain fine and clear. After this work has 
been done, the sides should be put into cold water over night to 
harden for splitting. The next morning they are ready to be 
split. This is done on the belt-knife splitting machine, shown 
in figure 56. In splitting the sides, a 6-oz. grain from the ma- 
chine will finish up 4| oz. of leather, as it loses 1^ oz. going 



132 PRACTICAL TANNING 

through the various processes. All loose ends and pieces of 
flesh should be trimmed from the sides before splitting is be- 
gun, so that there will be nothing to interfere with the hide 
feeding freely into the machine. After the sides are split, 
they should be run in a wash-wheel with cold water for a few 
minutes to open them up and to remove the glaze caused by 
the belt-knife. The grains and splits are next bated. 

Splitting out of aluminum sulphate and salt pickle. — 
Where hides are split out of pickle, a good procedure is to 
bate and pickle them with aluminum sulphate and salt in this 




Figure 57. — Rubber roll putting-out machine. 

manner: For every 100 lb. of sides, unsplit, and bated and 
washed, dissolve 4 lb. of sulphate and 10 lb. of common salt 
in 6 gallons of boiling water ; then add 6 gallons of cold water 
and use the liquor after it has cooled to 70° F. Drum the 
sides in this liquor for an hour ; then horse them up smoothly, 
and let them press and drain until the next day. 

Hides pickled in this manner should not be pickled pre- 
viously with acid and salt. If the splitting machine has a 
corrugated roll, the sides can be split right off the horse. If 
the machine has a smooth roll, the sides should be hung up 
to "sammie" (to become semi-dry), or pressed, or put out on 
a putting-out machine (figure 57), to prepare them for split- 
ting. The grains should be the same thickness that the finished 



DE-LIMING, DRENCHING, BATING, ETC. 133 

leather is to be, as they do not fall away like grains split from 
limed hides. Hides pickled with aluminum sulphate and salt 
split as easily as bark-tanned leather and the splits are as good 
as those taken from the limed hides. After the sides are split, 
the grains can be shaved while in the pickled condition, this 
saving putting them out for shaving after they are tanned. 
Both the grains and splits are then ready to be tanned. 

Splitting after tanning.— Tanning the sides in a chrome 
process and then splitting them is sometimes practiced. The 
sides are tanned in a one-bath chrome process in a paddle- 
wheel or by suspension, and when they are well struck through 
with the tan they are pressed and split. The pressing removes 
the surplus water and makes the leather drier and firmer. 
After pressing, the sides should be run in a dry mill until they 
are opened up and ready to be split, when they should be 
jacked the same as bark leather, and split to the thickness the 
finished leather is to be. After they are split, the grains are 
shaved and re-tanned. 

Splitting out of acid pickle.— When hides, are to be split 
in acid-pickled condition, they are allowed to drain 24 hours 
after being pickled, pressed to remove surplus liquor, and 
milled to remove the press-marks; they are then split to the 
required thickness. The grains can be shaved either after 
splitting or after they are tanned. 



CHAPTER V 

RAW HIDES: OIL AND ALUM TANNAGE 

Raw hide. — For certain purposes, such as drum-heads, sad- 
dle-tops, bayonet scabbards, belt-pins and the like, a very 
strong and stiff form of leather is required. To make such a 
product, the hides or skins are soaked, de-haired, and bated 
in the usual manner, and after thorough washing are carefully 
tacked on boards, the tacking being strong and close. The 
skins are then allowed to dry slowly, and as they dry contrac- 
tion takes place, causing a more or less transparent condition. 
When stripped, they are ready for market. When used, such 
skins are dampened with warm water and stretched into what- 
ever form desired. Parchment is usually made from selected 
sheepskins treated in this manner. 

For the manufacture of raw-hide pins, now used extensively 
for joining machinery belting, the hides are cut into strips, and 
while wet are twisted into shape and allowed to dry out under 
tension. Raw hide is also pressed into various shapes, such 
as hammer heads, washers, and the like. 

Lace leather. — Raw-hide lace leather must be strong and 
soft, so it is necessary to separate the fibers and lubri- 
cate them so that they will remain pliable. This is accom- 
plished by the following method : The hides are limed thor- 
oughly and bated with ammonium chloride. They are then 
given a light tawing by milling with 5 per cent of aluminum 
sulphate and 5 per cent of salt dissolved in just sufficient water 
to float the stock. When struck through, they are piled down 
for 48 hours, and then split to weight. The sides are then hung 
up to dry, and when well crusted they are dipped in lukewarm 
water and packed down to sammie. The sides, which should 
now contain about 30 per cent moisture, are placed in the mill 
in a mixture of 5 per cent of cod liver oil, with 2 per cent of 
tallow at 120° F. added: The drum is run for two hours, and 
another portion consisting of 3 per cent of cod oil and 1 per 

134 



RAW HIDES 135 

cent of tallow is added; and after another hour a similar quan- 
tity is added. When the sides have absorbed most of this oil 
they are set out on- the machine, and then well set by hand, 
using a dubbing of 2 parts cod oil to 1 part of tallow. The 
sides are then hung over sticks to dry. When the stock is 
dry, it is dipped in lukewarm water and piled down, care being 
taken that it does not become too hot. A certain amount of 
heat, however, should be developed to cause oxidation of the 
cod oil. The oxidized stock is now re-set by hand, again hung 
up, and finally rolled. 

In place of the cod oil and tallow, many tanners are now 
using a mixture of 50 per cent oleostearine substitute, 40 per 
cent of vacuum currier's wax, and 10 per cent of rosin, at a 
temperature of 140° F., using a total of 15 per cent of the 
mixture, and adding it in three portions as indicated above. 
Lace leather made by this process does not oxidize as quickly 
as that made from cod oil, and besides being less dangerous 
is less expensive. The same mixture is used for dubbing as 
for oiling, and the same procedure is carried out except in the 
case of packing down to oxidize. 

Shark-liver oil tannage. — Where cod-liver oil is used for 
stuffing or for other purposes the author has found that the 
oil from shark livers can be used with equally good results ; 
in fact, a stronger leather is produced with this oil than with 
cod or fish oils. 

Latigo leather.— A very strong leather, and one used ex- 
tensively .where strength and body are desired, is what is 
known as "latigo leather." The process employed in making 
this is essentially the same as for raw hide. The point of dif- 
ference lies in the fact that the sides, after splitting to weight, 
are run in a .paddle with a solution of . gambier of 15° bk. 
strength until the color is struck through. They are then dried 
out, sammied, and stuffed as described under raw hide. Some 
tanners improve the color of the stock by milling with a solu- 
tion of auramine or picric acid. 

Another method for making latigo leather is as follows: 
The hides are suspended in gambier liquor for a few days, 



136 PRACTICAL TANNING 

and then put into a solution of alum and salt. This process 
produces a thick grain which presents an excellent surface to 
the buffs. Stuffing is done with hard grease, degras, and cod 
oil. The leather is then shaved, buffed, and finally set out, first 
by machine, and then by hand. Tallow and oil are often used 
in stuffing lace leather, and when the grain is buffed off, there 
is, of course, no liability of its cracking and breaking when 
in use. 

Some tanners also run the stock in a paddle-wheel contain- 
ing a 15° bk. gambier solution and then finish with salt and 
alum ; while others run the sides in a mixture of alum, gambier 
and salt. In all cases they are finished by stuffing as de- 
scribed above. 

Alum-tanned lace leather. No. 1. — Put 30 lb. of alum and 
50 It), of salt into a clean barrel; add water, and boil with 
steam until the alum and salt are dissolved. Dissolve 6 lb. 
of sodium carbonate with hot water, and pour the liquor slow- 
ly into the alum and salt solution, which has been added to 
water in a paddle, plunging the liquor briskly Effervescence 
takes place when the soda solution is mixed with the alum 
liquor, and when it ceases, the liquor, to be in the right condi- 
tion for use, should have a sweetish taste. If it tastes sour, 
add dissolved carbonate of soda and salt in the proportions 
stated until it tastes sweetish or neutral. 

The liquor should be cold when the hides are placed in it. 
The tan liquor having been prepared, place about 400 lb. of 
washed sides into it. Run the sides 15 minutes after they have 
been placed in the liquor, again at the expiration of half an 
hour, and again at the end of the next half-hour, then at in- 
tervals of two hours until the close of the day. Frequent motion 
lays the foundation of an even tan and a uniform grain, two 
important considerations. 

On the second day the pack is in the liquor, run it 4 times 
at regular intervals; on the third day run it 3 times; and on 
the fourth day, twice ; and near closing time, haul the pack up 
to drain over night, and finish it the next day. 

Tanning may be done also by drumming the sides with the 



RAW HIDES 137 

liquor for one day, stopping the drum at intervals, and then 
starting it again. The pack being tanned and drained, hang 
the sides up for part drying. The spots that dry hard should 
be wetted with water, and the whole of each side made uni- 
formly moist and soft before grease is applied. Dampen the 
sides uniformly; fold and pack them in a box and let them 
remain 24 hours, when they are ready to be stuffed. The 
dubbing used to stuff the leather is made of pure tallow and 
neat's foot oil in the following proportions, according to the 
season of the year: In summer time, 10 lb. of tallow and 1 
lb. of neat's foot oil, and in winter, 10 lb. and 3 lb. respectively. 
The leather may be stuffed with tallow only, but the addi- 
tion of some neat's foot oil gives it a softer and mellower feel. 
Half a pound of rosin to 10 lb. of dubbing helps protect the 
dubbing from oxidation. The dubbing is applied in a fluid 
state at a temperature little higher than the melting point of 
the tallow, in the following manner : 

Place on a table the number of sides the stuffing-wheel will 
carry, and spread them out upon one another. With a swab 
or suitable brush give each hide a light coat of the fluid dub- 
bing on both flesh and grain. Place the batch in the cold stuf- 
fing-wheel, and set it in motion. The wheeling should be done 
in such a manner that the sides come into contact with the pins 
of the wheel, in order that the grease may be worked into 
the leather. 

When the sides have absorbed the grease, take them out of 
the wheel and hang them up until they are partly dry. Then 
with a stone having well-rounded corners go over the sides 
on the flesh side and straighten them out, when they are ready 
for shaving. Shave them lightly and evenly. Then coat 
both flesh and grain with melted dubbing, and run the sides in 
the wheel again. Hang the leather up, and when it is nearly 
dry, snuff it over with the currying knife on the flesh side; 
set the flesh out; stone, slick, and glass the grain; oil lightly 
on the grain, and hang up to dry. Then take the leather down 
and glass it on the flesh and brush it on the grain, when it is 
ready for use. 



138 PRACTICAL TANNING 

Alum tannage No. 2. — A tanning liquor for lace leather 
may also be made of 15 lb. of alum, 30 lb. of salt, and suf- 
ficient water to cover 50 sides, which are kept in this liquor 

24 hours. The liquor is then run off, and the sides are given 

25 lb. of alum and 50 lb. of salt, and handled twice each day. 
They should remain in the liquor two days, and then be hung 
up to dry. When dry, they are dampened down for 2 to 3 
days, and then worked out on the staker. To grease the sides, 
50 lb. of white tallow and two quarts of pine tar are mixed, 
and applied hot to both sides of the leather. The sides are 
then put into the drum, heated with steam to 85° F., and 
drummed one hour. They are next staked on the flesh side, 
stuffed again as before, and then set out lengthwise of the 
flesh and grain, and hung up to dry. Tanning can also be done 
in a drum in much less time than in a vat or a paddle. 

Alum tannage No. 3. — A process which is a little different 
from the preceding one is carried out as follows : After they 
are tanned with alum and salt, the sides are hung up and partly 
dried ; but are staked while a little damp, and then thoroughly 
dried. They are next stuffed by being given a coat of hot tal- 
low, applied liberallv until they will absorb no more. The 
leather is then run in a dry drum, stretched, and after rub- 
bing off the superfluous grease, is ready for use. 

Picker leather. — This leather is used extensively in cotton, 
woolen, and silk mills, and great care must be taken in its 
manufacture. It must be soft and mellow so that it can be 
tied into knots, and above all, it should be so tough that it will 
not tear or rip out where loops are cut into it to fasten onto 
the shuttle. The hides should be from good steer selection, 
weighing from 50 to 60 lb. each. They are soaked in cold 
water in the usual way, and when thoroughly soaked, are 
limed. When sufficiently limed, that is to say, when the short 
hair can be worked out, the sides are reeled into water at 95° 
F. This temperature should be maintained ; and the stock 
again reeled at the expiration of 24 hours. After remaining 
in this warm bath 48 hours, the hides are ready to be de- 
haired. Fleshing and bating follow, the hides being bated 



RAW HIDES 139 

down soft and silky. All the lime should be removed, and the 
hides should be soft, low, and clean, before they are put into 
the tan liquor. 

Gambier is preferable as a tannage, since it tans quickly and 
makes soft leather. Oak tannage also produces a soft, tough 
leather. The coloring must be done in paddle-wheels. The 
sides must be wheeled regularly, and the liquor gradually 
strengthened until the stock is thoroughly tanned. 

Lactic acid used in the first stages of coloring proves ad- 
vantageous. Rapid tanning results, by the proper use of the 
acid, and plump, yet mellow leather is obtained. This method 
is known as the oak-bark tannage, and it is suggested that 
when the hides fresh from the beam-house are put into the 
liquor, the latter should not be over 2° bk., and lactic acid 
is best employed for plumping after the third day of tanning. 
Gambier-tanned picker leather is treated in the same manner 
as oak leather in the first stages of tanning, or until the grain 
and flesh are nicely struck through with tannin. The sides 
are then ready for a special treatment, which forms a yellow 
streak in the center of the hide. 

The gambier liquor is made of about 4 per cent alum and 1 
per cent salt, and sufficient gambier to give a bright orange 
color. This bath is heated to 90°F. At the end of an hour, 
draw the sides out and return them to the liquor, and in 2 
hours repeat the treatment, and again in 3 hours. The fol- 
lowing day raise the leather and put it back again, and let it 
remain for 24 hours, then hang it up and sammie quickly. 
Put the sides into a stuffing-wheel, together with all the tal- 
low they will take — say, 4, 5, or 6 lb. — until all the tallow 
has gone into the stock. The sides should now be set on the 
machine, then re-set by hand, and given a good coat of dub- 
bing made of tallow and sperm oil, about 60 per cent of the 
former to 40 per cent of the latter. The tallow should be al- 
lowed to cool until one's hand can bear the heat, or until a 
slight skin arises on the surface of the tallow. The sperm oil 
may now be added, the tallow being stirred constantly while 
the oil is poured in slowly. This makes a fine, close dubbing, 



140 PRACTICAL TANNING 

and both oil and tallow will penetrate. Should the oil be 
added while the tallow is hot, it will result in what curriers 
call "fish eggs," and only the oil will penetrate the stock, 
which is very undesirable. The leather is then dried and 
worked out soft and clean. 

Pyro tan. — A process recently introduced into the United 
States consists of treating side leather, kips, or skins, with 
a solution containing aluminum sulphate, salt, and sodium 
pyrophosphate. The stock is de-haired, bated, and pickled in 
the usual manner, and is then milled in a solution, sufficient 
to float the hides, containing 10 lb. of aluminum sulphate, 5 
lb. of salt, and If lb. of sodium pyrophosphate for each 100 
lb. of stock taken. The mill is run continuously until tan- 
nage is complete, which occupies from 5 to 10 hours, accord- 
ing to the weight of the pelts. The leather may be finished 
at this point by fat-liquoring, drymg-out, dampening-back, 
staking, etc. The usual procedure, however, is to re-tan in 
gambier or quebracho, and finish as indicated under vegetable 
tanned leather. 

In working with this process, the author has found that 
it may be used as a pre-tannage for one-bath chrome treat- 
ment. The leather thus secured has fine body and excellent 
tensile strength. It may be finished as given later under 
chrome tannage. The author has also found that the com- 
bination may be used to advantage as a pre-treatment in the 
manufacture of oil-tanned lace or glove leather. 

Chamois leather. — At the present time this is made almost 
exclusively from sheepskins. It is produced by the action of 
oil upon the raw skins, and is distinguished from all other 
classes of leather by remarkable softness and open texture. 
After the wool is removed, the skins are limed long and 
thoroughly; they are then split on a machine, the grains being 
tanned and finished into fancy leather, and the flesh splits into 
oil-tanned or chamois leather. The splits are de-limed, 
washed, and pressed to rid them of the surplus water and to 
make them as dry as possible. 

To soften them, the skins are thoroughly beaten by a ma- 



RAW HIDES 141 

chine, after which they are sprinkled with cod oil, and again 
beaten to force the oil into the leather. The best grade of 
Newfoundland cod-liver oil is considered most suitable. Oil- 
ing and beating the skins is repeated 2 or 3 times, or until 
they have assumed a mustard color. They next undergo a 
process of heating, by which the oxidation of the oil, begun 
during the previous process, is completed. The heat is gen- 
erated spontaneously. The skins must be watched closely and 
should be turned over frequently. When the temperature gets 
too high, the leather is seriously damaged. The highest tem- 
perature allowable is 130° F. When oxidation ceases, and the 
skins are no longer susceptible to heating, they are treated 
to remove the oil. This is done by washing them in hot 
water and then squeezing in a hydraulic press. The grease 
squeezed out in this way, is called "degras," and is used by 
tanners. The oil remaining in the skins is removed by wash- 
ing them in a solution of soda ash, which causes the fatty 
acids to saponify. This saponified oil is then neutralized 
with sulphuric acid and forms what is known as "sod oil." 
A certain amount of the oil should be allowed to remain in 
the skins to give them softness. 

The finishing process consists of staking and smoothing 
down all unevenness on the surface. The skins may be 
bleached or colored, as may be desired. 

Bleaching. — Chamois skins may be bleached by exposing 
them to direct sunlight. They are first treated with 2 per 
cent solution of a neutral soap, then wrung out, rinsed, and 
exposed to the sun for a day. A second washing with a 1 per 
cent soap solution is given; the skins rinsed, and again ex- 
posed to the sun. This process is repeated until the skins are 
bleached satisfactorily. Washing may be done with soda, but 
this has a tendency to make the leather harsh; soap is there- 
fore preferable. 

Chamois leather is bleached rapidly and uniformly by im- 
mersion first in a solution of potassium permanganate and 
then in sulphurous acid. Before it is bleached, the excess of 
oil must be removed by washing in a lukewarm 2 per cent 



142 PRACTICAL TANNING 

solution of a neutral soap; the skins are then rinsed and wrung 
out. The solution is prepared by dissolving 1 lb. of perman- 
ganate in 5 pints of water. Enough of this solution is added 
to water in a tub to color it a deep purple. The bath is then 
warmed up to 100° F., and the skins are placed in it, one at 
a time, and stirred for 20 minutes, after which they will be 
found to be thoroughly permeated with the solution. 

The first bath can also be prepared by using 1 oz. of 
potassium or sodium permanganate for each dozen skins. 
Then sulphuric acid to about one- fourth the weight of the 
permanganate is added, and the skins thrown in. 

After the permanganate bath, the skins are rinsed in cold 
water and placed in a solution of sulphurous acid. The tub 
should contain water into which gaseous sulphurous acid is 
either conducted from a steel cylinder, or liquid acid is added 
until the brown color of the stock has disappeared and the 
skins are bleached. The goods are stirred in the acid for 15 
or 20 minutes, or until they are white; they are next rinsed 
in cold water to remove the acid, and are hung up to dry. 

Sulphurous acid may be prepared as follows: Dissolve 14 
lb. of sodium bisulphite in 15 gallons of water. Into another 
vessel containing 2\ gallons of water, pour 6 lb. of muriatic 
acid, and mix well. The skins are placed in the bisulphite 
solution, and the diluted acid is added slowly until the skins 
are bleached throughout. They are then washed thoroughly, 
dried, and finished. 

The second bath may be prepared by adding 3 per cent of 
sodium bisulphite to sufficient water, or about 3^ oz. per 
dozen skins, and after the goods have been in the solution 
15 minutes, muriatic acid, one-third of the weight of the soda, 
is diluted with water and added slowly to the liquor. After 
the skins have been bleached and washed they are washed in 
a solution of white castor-oil soap or olive-oil soap, and are 
then dried and finished by staking and pumicing. 

Rogers' shark-liver oil process. — In his work on shark- 
liver oil, the author has found that this material may be used 
to advantage as a substitute for cod-liver oil, and in many 



RAW HIDES 143 

cases gives even better results than this commonly used prod- 
uct As previously mentioned, it can be used for straight 
oil tannage, but a method which has given very satisfactory 
results is covered by U. S. Patent No. 1,346,385, granted 
July 13 1920. In working with this process, the stock is 
depilated and pickled in the usual manner, and is then run in 
a drum with 7 per cent of aluminum sulphate, 5 per cent of 
salt and 2 per cent of borax. When well tawed, the stock 
is h'orsed-up over night, set out, and hung up to dry. When 
thoroughly dry it is dipped in lukewarm water and piled 
down to sammie. When properly damp, the hides, splits or 
skins are placed in the drum and run for 2 hours with 5 
per cent of shark-liver oil. A second lot of 5 per cent of 
this oil is then added, and after an hour, 3 per cent more 
and after another hour, another 3 per cent. At the end of 
the day the hides are placed in piles to temper. The follow- 
ing day the stock is well set out on the machine. If to be 
used for lace leather, the hides are given a dubbing of shark- 
liver oil and tallow in the proportion of 3 to 1 ; if for chamois 
leather, no dubbing is applied. In each case the stock is 
huncr up to dry, and when thoroughly dry the stock is piled 
down tightly to oxidize. Care must be taken that it does not 
become too warm. To hasten the oxidation the skins may 
be slightly dampened before piling. As the oxidation reaches 
the limit the stock is milled in the drum or stocks, and again 
hurtg up to dry in a warm room. If lace leather is desired, 
the hide should be well set before drying and after drying 
should be rolled on the jack. 

For -love or chamois leather the skins are not set out, 
but after drying are milled with a solution of sodium car- 
bonate, well washed, and dried. The dried skins may then 
be staked and buffed, and are ready for market. _ 

Sheepskin fleshers.— When sheepskins are split out ot 
lime the grains are de-limed and tanned in bark, sumac, or 
some other tannage, and finished into skivers; the splits or 
flesh portions are made into chamois leather and used for 
linings, gloves, and other purposes; they are also tanned in 



144. PRACTICAL TANNING 

other ways and used for various purposes where inexpensive 
material is required. Any one of the alum tannages for 
whole skins can be used in tanning the splits. Tanned with 
alum, salt, egg-yolk, and flour, they make very soft stock 
which can be used in the white or colored any shade. The 
chrome process can also be used, the splits being fat-liquored, 
dried, and staked in the usual manner. A formaldehyde tan- 
nage can also be applied : For each 100 parts of pelt, 1 part 
of commercial formaldehyde in the necessary quantity of 
water is used. The skins are left in the liquor from 12 to 24 
hours, and are then neutralized, washed, and fat-liquored with 
6 parts of soft soap, thus making a very soft leather resembling 
chamois skin. Yellow stock is obtained by using moellon in- 
stead of soap as a fat-liquor. 

Imitation castor. — A process for sheepskin splits, which 
produces stock closely resembling castor or Mocha leather, 
is carried out as follows, the quantities of materials being 
sufficient for 2 dozen fleshers of ordinary size : The goods 
are immersed, stirred, and pounded for 30 minutes in a solu- 
tion of 1 lb. of alum, \ lb. of flour, \ lb. of oatmeal (or 1 lb. 
of either alone), \ pint of olive-oil and sufficient water to 
process nicely. Tanning can be done in a drum in about 50 
minutes. 

The goods are then immersed for a half hour in a solution 
consisting of \ pint of ammonia, |- bar of soap, \ oz. of soda, 
\ lb. of salt, and 2 oz. of whiting or ocher, all boiled in \\ 
gallons of water. To this solution is added either 1 lb. of 
flour or 1 lb. of oatmeal mixed in 6 quarts of water. The 
fleshers are drummed in this mixture for 30 minutes, after 
which they are dried, worked soft, and finished on either 
side. The skins dressed in this manner are very soft, pliable, 
elastic, and strong. After having been treated by the first 
part of the process, they may be dried and finished, yet it 
is desirable to use the entire process, as they are thus given 
a superior quality and capacity for a better finish. 

Another excellent process is as follows : The splits, drenched 
and free from lime, are put into a drum together with a 



RAW HIDES 145 

solution of 12 oz. of alum and 4 oz. of salt in a half pail 
of water, and drummed 30 minutes. Then 1 pail of flour is 
added for each 10 dozen skins, and 1 quart of fresh egg- 
yolks, and the drum run for 30 minutes longer. Take the 
skins out of the drum and hang them up to dry; put them 
away in a dry, cool, place for a few weeks, then dampen and 
mill them in flour, knee-stake them, and run them on a fine 
emery wheel After this has been done, wash the skins, and 
if they seem to require it, give them 1 to 2 quarts of egg- 
yolk to 12 dozen skins; dry them again, and stake out soft. 
The finished skins should be very soft and white. They can 
also be colored any shade desired. 

White calfskin leather.— Soft, tough white leather is 
made by tanning calfskins by the following process: The 
skins are limed, bated, and pickled in the usual manner and 
are then allowed to drain 24 hours. 

Tannage.— To prepare the tanning liquor boil 12 lb. of 
aluminum sulphate in 10 gallons of water. Dissolve 24 oz. 
of bicarbonate of soda in a pail, and pour the solution slowly 
and with constant stirring into the sulphate solution. Allow 
the resultant white liquor to cool to 80° F. Put the pickled 
skins into a drum, together with 10 gallons of water, 1 lb. 
of Glauber's salt, and 3 lb. of common salt for 100 lb. 
of skins. Drum the skins 20 minutes with the solution, then 
drain off the liquor. Put 10 gallons of lukewarm water and 
6 lb. of salt into the drum together with the skins, and let 
the machine rotate 10 minutes. Then pour half of the sul- 
phate-soda solution into the drum, and drum the skins 3 
hours. At the expiration of that period, take the leather out 
and let it drain until the next day; then hang it up to dry. 
When dry, put the skins back into the drum, together with 
8 gallons of water, and run them 10 minutes; then add the 
rest of the white liquor and run the drum 2 or 3 hours. Place 
the leather over horses to drain at least 12 hours, then hang 
up to dry. 

Fat-liquoring.— -When dry, let the leather lie in the crust 
state in a clean dry room for some time, the longer the better ; 



146 PRACTICAL TANNING 

then dampen it with warm water preparatory to fat-liquoring. 
Sulphonated castor oil or acid fat-liquor is the material to 
use, as it imparts softness without discoloring the leather 
or making it greasy. For each- 100 lb. of dry leather use 
7 lb. of the oil, and stir it into 10 gallons of water at 95° R 




Figure 58.— Buffing machine, used for snuffing grain 
for ooze, and flesh for suede leather. 

until it is dissolved. Put the moistened leather into the drum; 
start the machine, and pour the solution of oil through the 
gudgeon, and drum the leather 40 minutes; then let it drain 
over night. The next day strike out the grain and apply 
a mixture of French chalk (talc), 2 parts of glycerine, and 
4 parts of water. Apply this to the grain and then hang 
the leather up to dry. 

Finishing. — This process consists of moistening the leather, 
staking, and tacking it on boards. If it is not soft enough 
when dry and taken from the boards, re-stake it; if staking 
does not soften the leather sufficiently, wet it and give it more 
fat-liquor. The appearance of the flesh can be improved by 
buffing on a carborundum wheel (figure 58) ; and the leather 



RAW HIDES 1^7 

can be finished on the flesh if such flesh-finished leather is 
desired 

Another process of making white calfskins employs an 
alum tannage composed of aluminum sulphate, salt, flour, egg- 
yolk, and oil. The proportions given are based on 100 lb. of 
pickled skins. Make a paste of 5 lb. of flour and a little 
water. Dissolve 3 lb. of sulphate and 5 lb. of salt in 10 
gallons of water. Slowly add 4 oz. of bicarbonate of soda, 
and then mix in 2 lb. of egg-yolk and 2 lb. of olive oil. Add 
the flour paste and drum the skins 3 hours in the mixture. 
Leave in the liquor over night, drum a few minutes the next 
morning, and dry at a moderate temperature. 

Finishing consists of staking and buffing the skins, drum- 
ming them with 1 lb. of egg-yolk and 5 lb. of talc ; then set- 
ting out, tacking, and drying. If colored leather is 
desired, the grain can be colored by hand, leaving the flesh 
white; or a drum can be used and the leather dyed through- 
out. This class of leather is, as a rule, dyed with wood 
colors, which may be shaded with acid colors. Another 
method is to bottom the leather with wood colors and then 
top with basic colors. 

Formaldehyde tannage. — By a method of tanning with for- 
maldehyde, white skins are obtained which are very similar 
to alum-tanned goods. The beam-house processes are carried 
out as usual ; the skins are next washed in tepid water, when 
they are ready for the tannage. For this a solution of 2\ 
parts of commercial formaldehyde in 100 parts of water is 
used. This liquor is prepared in a paddle, and the skins are 
put in and left there from 24 to 48 hours; then withdrawn, 
neutralized, washed, and fat-liquored with a liquor made of 
100 parts of neat's foot oil, 25 parts of carbonate of soda, 
and 500 parts of water. The skins are drummed in this for 
an hour, then dried and finished. Sulphonated oil can be used 
for fat-liquoring, with good results. Fat-liquoring with moel- 
lon degras gives skins of a light yellow color. 

Kid glove leather.— -The tanner who wants to make Mocha 



148 PRACTICAL TANNING 

or castor glove leather will find the following process satis- 
factory : The skins, after they have been soaked and softened, 
are fleshed and limed. Liming should be done in clean white 
limes containing no red arsenic or sodium sulphide. The 
first lime should be clean, white, and weak, the skins being- 
passed from it into stronger lime and limed thoroughly; or 




Figure 59. — Buffing wheel. 

a gathering lime may be used by hauling the skins out each 
day and adding fresh lime. The period in the lime varies 
from 20 to 40 days according to the judgment of the tanner. 
When the hair comes off easily, the skins should be de-haired 
and the grain frizzed. After frizzing, put the skins in weak 
lime water for 2 or 3 days, then wash them in warm water 
and drench with lactic acid in a drum, 100 skins requiring 
about 1 quart of acid in 10 pails of water at 90° F. Drum 
the skins in this solution for an hour, and rinse. 

Another process, using alum, salt, egg-yolk, and flour is as 
follows: For each dozen skins dissolve 12 oz. of alum and 
4 oz. of salt to make 1 pail of liquor, and drum the skins with 
this solution for 30 minutes; then add 1 pail of flour for each 



RAW HIDES U9 

10 dozen skins and 1 quart of fresh egg-yolk, and drum the 
skins 30 minutes longer. Take them out of the drum and 
hang them up to dry. When dry, put them away m a dry, 
cool place for a few weeks to give them time to become com- 
nletely tanned. To finish the skins, dampen and null m flour, 
next knee-stake them, dry again, and then run them on a flue 
emery wheel. After this has been done, wash them with 
emery wneei. e „„. yo lk to 12 dozen skins, 

water and give them 2 quarts ot eg y" 
Then dry them again, knee-stake and finish on the finest 
emerv The skins should now be very soft, dry, and white 
and can be used for white gloves without further treatment, 
colored skins are desired, they can easily be colored any 
shade, then dried and staked, and finished on a buffing wheel 
as shown in figure 59, using the finest emery. This process 
an also be us°ed for grain-finished skin. For. such goods 
however, it is best to use arsenic with the lime and a dung 
bate to de-lime the skins. The leather finishes soft and strong, 
and has a fine appearance. 

Another good formula for pickled sheepskins which pro- 
duces nice white, soft, and "well-fed" leather is as follows , 
For 1 dozen skins, 1 lb. of alum, 1 lb. of salt, | pint of egg- 
yolk, and 1 lb. of flour are used. The alum and salt are dis- 
solved in hot water. The flour is mixed with cold water, 
the egg-yolk is added, and the whole is thoroughly stirred. 
The solution of alum and salt and the mixture of egg-yolk 
and flour are put into the drum together with the skins, and 
the whole drummed for 2 hours. The skins are left ,n the 
liquor over night, then dried out. One to two gal ons of 
warm water are used with the tanning materials for 1 dozen 
skins. This tannage should not be used on skins in the 
pickled condition, but if such skins are to be tanned with 
it the pickle should be removed by a light sour drench of 
bran and salt, or bicarbonate of soda and salt. ■ 

One dozen small lambskins for glove leather can be tanned 
with i lb. of alum and * lb. of salt. Dissolve the alum and 
salt together, making a half pail of liquor. Drum the skins 
with this solution for half an hour: then add 1 pad of good 



150 



PRACTICAL TANNING 



flour to each 10 or 12 dozen skins, and 1 quart of egg-yolk. 
Run the drum a half -hour longer, then hang the skins up to 
dry. After drying, lay away for a while to age. Next 
dampen the skins and drum with a little flour, then knee-stake 
them (figure 60), wash, and give them 2 quarts of egg-yolk 
to 12 dozen skins. Dry again, stake, and finish. The skins 
should be taken from the drench and tanned without pickling. 
If pickled, drench them in sour bran or bicarbonate of soda 
to remove the acid. 

Sheepskins taken from the drench or 
de-pickled in a bath of sour bran and 
salt can be alum-tanned in the following 
manner: For every 100 lbs. of skins, 
3 ltf. of aluminum sulphate and 6 lb. of 
salt are dissolved in 6 gallons of water. 
This liquid is put into the drum with 
the skins, and the drum is run 30 min- 
utes. A solution of 10 lb. of sodium 
hyposulphite in 5 gallons of warm 
water is poured into the drum, and the 
skins are drummed in the combined 
solutions for 20 minutes. The hypo- 
sulphite fixes the tannage on the fibers 
of the skins, and also thins the goods. 
In order to overcome this thinning, 
another solution of 2 lb. of aluminum sulphate and 4 lb. 
of salt in 3 gallons of water is added to the contents of 
the drum, and the drumming is continued for another 
half -hour, or until the skins have become plump. The next 
operation is rinsing in clean water and allowing the leather 
to drain several; hours, then drying it out. Skins of fine tex- 
ture and grain are obtained by this process. It is very essen- 
tial, however, that the skins be entirely free from acid and 
perfectly neutral when the process is begun, otherwise they 
will be imperfectly tanned. After the skins have dried, they 
may be made softer by drumming in a warm solution of sul- 
phonated oil. Flour may be added to the oil. The leather 



gG^ 




Figure 60.— Knee-staker. 



RAW HIDES 151 

can also be washed back and tanned with a one-bath chrome 
liquor, and finished in any manner desired. White chrome 
leather is secured by bleaching the skins with borax and sul- 
phuric acid, and fat-liquoring with sulphonated oil and flour. 
Alum-tanned skins should be buffed on the flesh side on an 
emery-wheel to get rid of all loose flesh and make them soft 
and smooth. In any alum process, flour increases the soft- 
ness and plumpness of the skins, and makes the grain less 
liable to crack. The cost of tanning is of course increased 
by using flour, but the better quality of the leather is suffi- 
cient to offset the added expense. 

White pigskins.— If white pigskin leather is required, the 
skins should be tanned in an alum and salt tannage or with 
aluminum sulphate. It is also practicable to tan them with 
formaldehyde, as with calfskins. The white leather can be 
finished in the white and can also be easily colored light and 
fancy shades. Thorough work in the beam-house is im- 
portant for such leather. Not only must the skins be soaked 
in sal-soda water and worked over the beam to rid them of as 
much grease as possible, but they should also be fairly heavily 
limed and bated, and then worked out again so as to be as 
clean as possible before tanning is started. If they are not 
too full of holes, pickling and tanning can be done most ad- 
vantageously in a drum. To pickle 100 lb. of pigskins, use 
1 lb. of sulphuric acid, 15 lb. of salt, and 15 gallons of water, 
and drum the skins in this liquor 1 hour ; then place them over 
a horse to drain 12 hours before tanning. 

Prepare the tan liquor by boiling 12 lb. of aluminum sul- 
phate in 10. gallons of water. In a pail dissolve 1| lb. of 
bicarbonate of soda by boiling in 1 gallon of water. Pour the 
soda solution slowly and with constant stirring into the sul- 
phate solution; care must be taken to pour the soda solution 
in carefully, for if it is added too rapidly the tan liquor will 
be spoiled. The mixture should be used cold. 

Tanning is effected as follows: Put the pickled skins into 
a drum, together with 10 gallons of water, in which 1 lb. of 
Glauber's salt and 3 lb. of common salt have been dissolved, 



152 PRACTICAL TANNING 

these quantities being used for 100 lb. of skins. Drum them 
with this solution 20 minutes; then stop the drum and drain 
off the liquor. Put the plug back, and throw in 10 gallons 
of water at 75° F., and 40 lb. of salt; start the drum and 
run it 15 minutes. At the end of this period, pour half of 
the sulphate-soda solution into the drum and run 3 hours. 
Drain the skins over a horse until the next day, and then 
hang them up to dry. When dry, put them back into the 
drum, together with 8 gallons of water and run 10 minutes; 
then add the other half of the sulphate-soda liquor and run 
the skins in it 3 hours. Drain them 24 hours, wash in clear 
water, and fat-liquor with acid fat-liquor. Drumming the 
skins with flour is another way to make them white. The 
leather is washed after tanning and then given the flour treat- 
ment; about 50 lb. of flour made into a thin paste with water 
being required for 100 or more skins. The leather is 
drummed 2 hours in the flour, and is then fat-liquored and 
dried. 

Finishing consists of staking the leather and milling it with 
powdered chalk or soapstone, after which it is ready for use. 
The flesh should be buffed clean and smooth, and if a leather 
without a grain is wanted, the grain should be removed either 
in the beam-house or by burring on an emery or carborundum 
wheel. 

Tanning snake skins with alum and salt.— The skins of 
snakes, like all other skins, should be soaked in water until 
they are soft, then broken or fleshed on the beam, and put 
back into the water for a few hours. They are then pickled 
with sulphuric acid and salt, after which they are placed in a 
solution of equal parts of alum and salt, in which they remain 
over night or longer. A basic solution of aluminum sulphate, 
as described for alum-tanned sheepskins, may be used for 
tanning. The skins are hung up to dry, and then are run with 
moist sawdust until ?11 the scr.les are off; they are then worked 
out carefully and dried. Some tanners prefer to remove the 
scales by liming in the usual manner. 

White splits. — Where a soft white split is wanted, a tan- 



RAW HIDES 153 

nage of aluminum sulphate may be used. If the sides are 
split out of the limes, the splits should be bated and pickled 
with sulphuric acid and salt as with grains or whole hides; 
they are then in condition to be tanned. The tanning liquor 
is prepared and used as under white pigskins. 

Finishing consists of drumming the splits with a solution 
of sulphonated oil, 7 lb. being used in 8 gallons of warm 
water for 100 lb. of dry splits. Some flour may be added with 
advantage to the oil solution. When the leather has dried 
again it is staked and run in a dry mill until it is perfectly 
soft. The solution of oil may be added to the tanning liquor, 
which saves the labor of the extra fat-liquoring. 

Formaldehyde also produces white leather. The splits are 
tanned in a formaldehyde liquor as with grains and sheep- 
skins, then neutralized and fat-liquored with soft soap or sul- 
phonated oil, dried, and finished. 

Splits for white shoes. — For sporting and athletic shoes, 
seal splits are frequently sold as a good imitation of the real 
deerskin article. These goods are treated as already de- 
scribed so far as soaking, liming, bating, and drenching are 
concerned. Only the best and stoutest splits are selected for 
this purpose. After drenching, the splits are washed in warm 
water and placed in a pickle made as follows: For every 100 
lb. of splits, thoroughly dissolve 20 lb. of alum and 14 lb. 
of salt. Use at 95° F., and drum the goods with it one hour. 
Then add a mixture of flour, egg-yolk, and china clay, made 
as follows: Mix 35 lb. of flour with enough water at 95° F. 
to form a fairly stiff paste, and add | gallon of egg-yolk and 
about 5 lb. of clay. No oil or grease is necessary, as seal 
splits are naturally greasy. 

To apply this dressing it is best to stop the mill and add 
about half of the paste to the goods. Drum 15 minutes, then 
add the remainder of the paste, and run 2 hours. Next take 
the splits from the mill, double them across, and spread them 
out in a vat or tub. The liquor in the mill is then poured 
over them and they are allowed to lie in this for 3 days, haul- 
ing up once a day and allowing to drain. After the final 



154. PRACTICAL TANNING 

draining, tack on frames or boards and dry quickly. If this 
is not done the result will be poor, as the alum and salt will 
not be fixed properly, and the finished leather will be flat 
and tinny. 

The splits are now allowed to lie in a cool place for 2 or 
3 weeks to feed and mellow, and they are then staked. Damp 
down first by draining through the liquor they are in, after 
making up a convenient quantity with water. Stack them in 
a pile until they are in good condition for staking, which is 
best done by hand, although machines do good work. The 
splits are then dried and worked on the perch with the arm- 
crutch stake. Next carefully run them on an emery wheel, 
commencing at the butt and work about halfway across, and 
then turn them and do the other side in the same manner. 
Turn over, and repeat the operation as before, and a fine, 
velvety fiber will result. After being again placed in the 
perch, rubbed over with whitening, and finally worked out 
well with the hand-scouring tool, the splits are ready for the 
shoe manufacturer. 

Tanning buckskins. — The preparatory treatment of deer- 
skins is somewhat similar to that for sheepskins. Green 
skins are soaked for a few hours and fleshed. As they are very 
buoyant and will not stay under the water, it is necessary to 
place a weight on them to keep them submerged. For dry 
skins a sulphide soak should be used and the skins thoroughly 
softened before they are put into lime or coated with depila- 
tory paint. 

Two methods can be followed for removing the hair : The 
skins may be painted with a mixture of lime and sodium sul- 
phide, or one of lime and red arsenic, as for sheepskins; then 
de-haired and limed a few days. Another method is to place 
the skins in lime as for calfskins, using lime and sodium sul- 
phide; de-hairing in the usual manner, and then bating the 
skins. 

De-liming is effected by bating or drenching the skins with 
the same materials used in de-liming sheepskins; the goods 
then pickled and tanned. 



RAW HIDES 155 

White buckskin. — A well-tanned, soft, and white' buckskin 
is obtained by tanning with a solution of basic aluminum sul- 
phate, as under white pigskins. Dampen, stake, and dry the 
goods, then buff and drum with 2 lb. of egg-yolk or sul- 
phonated oil and 5 lb. of talc. Set the leather out, tack, and 
dry. Any shade of color — gray, tan, etc. — can be obtained 
by ordinary application of suitable wood dyes or artificial 
dye-stuffs. 

A white leather is also made by tanning the skins with 
formaldehyde; and by adding a little moellon of the first 
quality to the soap fat-liquor, very supple skins of a light yel- 
low color are obtained. Neat's foot oil and cod oil, as well 
as sulphonated oil, produce white skins. The skins are left 
in the liquor from 24 to 48 hours, when they are neutralized, 
washed, and fat-liquored with soap for white leather; or with 
soap and moellon, or moellon alone, for a yellow shade. 

Where the grain has been removed, the skins tan rapidly. 
The leather resembles alum-tanned goods, being of good white 
color, soft, and supple. Sulphonated oil serves as a fat-liquor; 
so does soap and moellon. Finishing consists of staking and 
working out. 

Indian method of tanning buckskins. — The North Ameri- 
can Indians have for ages dressed deerskins into leather, and 
the leather made by them is renowned for toughness and 
durability. A description of their method of dressing is of 
interest : 

According to John Motheral in the "Leather Manufac- 
turer," the skins are fleshed and all flesh and membrane re- 
moved. It is then soaked in water to swell and free it from 
blood, when it is ready for graining, which is done with a 
case-knife or a butcher's knife on a beam having a diameter 
of 6 or 8 inches. This way of removing the hair and the 
grain makes Indian-dressed buckskin of the highest class. 

Another way of preparing the skin for graining is, after 
the skin has been fleshed and soaked, to treat it with a weak- 
lye for 2 or 3 days, and then grain it. But this does not 
yield a product equal in toughness to that by the former 



156 PRACTICAL TANNING 

method. The skin being grained, is then ready for the tan- 
ning or tawing process, which is done with the brains of the 
deer or those of cattle, horses, hogs, etc. 

Briefly, the brains are prepared by putting them into a bag 
of loosely woven cloth, and boiling them an hour in soft 
water. The water is then poured off into another container, 
and cooled until one's hand can bear the heat. The bag is 
rubbed between the hands under this water until the brains 
are forced through the cloth. The buckskin is then kneaded 
and stretched in the liquor for an hour, at intervals of 10 
minutes; and is allowed to soak for 2 hours (over night in 
winter) followed by more kneading and stretching. The 
skin is then partly dried, after which it is stretched every way 
until dry, folded, wrapped, and put away for 2 weeks or more. 
The skin is now ready for the smoking process, which colors 
and re-tans it, bringing it into condition whereby it may be 
washed with soap, yet it dries soft. Smoking is done with a 
slow fire of decayed wood, and is continued on both sides 
until the color is light yellow to yellowish-brown. The In- 
dian stretches the skin over the end of a barrel, and conducts 
the smoke to it; but a smoke-house, such as used for curing 
meat, will do as well. After being smoked, the skin is 
scoured with soap in lukewarm water, rinsed, dried for a 
week, dipped in water for a few seconds, folded, and covered 
for a half day, stretched, and dried. The skin is then soft 
and pliable. 

Tanning with formaldehyde. — By the application of the 
following process of tanning hides or skins, a leather is ob- 
tained which will not lose its tannage through the action of 
hot water or sweat. It is also very tough and resistant to 
tension, being especially adapted for orthopedic and surgical 
uses, such as belts, straps, linings, envelopes, gloves, and even 
for saddlery and shoemaking. 

The leather is prepared by a combined tannage of formal- 
dehyde, grease or oil, and a watery emulsion containing mag- 
nesium silicate. This emulsion contains the active parts in 
extremely fine division, in order to favor as much as possi- 



RAW HIDES 157 

ble the contraction and binding of the surface. The skins are 
prepared in the usual manner by liming, bating, and washing, 
and are then placed in the drum, together with the emulsion, 
which must be sufficient to cover them. 

The tanning can also be done in stationary tanks, but this 
takes more time. At the beginning, the emulsion is composed 
preferably of 20 per cent oil, 5 per cent talc and \ per cent 
formaldehyde. A durable fat emulsion is first prepared for 
which any of the water-soluble (sulphonated) oils may be 
used The addition of gum tragacanth or similar binding sub- 
stances to the emulsion is not absolutely necessary, if care is 
taken to neutralize the small amount of free oleic acid present 
in the oils, by adding about 10 drops of soda solution to each 
quart of the emulsion. About one or two times the quantity 
of formaldehyde given, as may be required, is added in the 
course of the tanning. The length of time needed to tan 
the skins depends upon their thickness. Several days are 
required for thin leathers where stationary tubs are used; 
thick skins require from 2 to 3 weeks. Where a drum is 
used thin skins can be tanned in 24 hours. 

All kinds of skins can be tanned by this method; and it 
may either before or after tanning, be used in combination 
with any other tannage. Leather made by this process dif- 
fers from chamois in its color and greater strength, and it 
does not shrink even after repeated washing. 

This leather, which is similar in appearance to tawed leather, 
maintains-even when 3/16 inch and more thick, perfect pli- 
ability and suppleness, together with great firmness, which 
enables it to fit itself wherever worn. 



CHAPTER VI 



CHROME TANNAGE 



The action of chromium salts upon hide substance was first 
studied by Knapp in 1858, but his investigations led him to 
conclude that their application was of no practical value. Al- 
though other investigators took up the matter, it was not until 
1884 that any really important advance was made. At this 
time Augustus Schultz patented his "two-bath process," in 
which skins or hides are treated with a solution of chromic 
acid, produced by the action of hydrochloric acid on sodium 
or potassium dichromate, and afterwards with a solution of 
sodium thiosulphate and hydrochloric acid. The hide substance 
takes up the chromic acid, which is subsequently converted 
to the basic condition by means of the "hypo." In 1893, 
Martin Dennis made a study of the action of chromium salts 
as previously investigated by Knapp, and perfected a method 
for "one-bath tannage," for which he was granted numerous 
patents. 

Two-bath chrome process. — While the details involved in 
the application of this process vary, nevertheless chrome tan- 
ning is uniformly carried out either in a paddle or drum. 
Different kinds of leather require different percentages of the 
chemicals. In the drum tannage, 6 per cent of sodium di- 
chromate and 3 per cent of hydrochloric acid, regulated on 
the weight of the wet skins, are mixed with sufficient water 
for the proper handling of the stock. The skins or hides are 
placed in the drum, and the chrome solution is added, while 
the drum is kept in motion. The hides or skins are worked 
in the solution until they have taken on a uniform yellow 
color and are completely struck through. They are now re- 
moved from the drum and freed from the superfluous liquor 
either by horsing up over night or by putting out; the latter 
operation may be done by hand or on the machine. After 
standing for 24 hours, the chromed stock is returned to the 

158 



CHROME TANNAGE 159 

drum and run for about 1| hours with a solution of 12 per 
cent of sodium thiosulphate and 6 per cent of hydrochloric acid. 
On removal from the drum the stock should have a blue- 
green color and should be uniform throughout. If thoroughly- 
tanned, no curling will take place when a strip is placed in 
boiling water. The stock is horsed up for 24 hours to allow 
the chrome to set. It is then neutralized by running for 30 
minutes in a | per cent sodium bicarbonate solution, washed 
in running water 30 minutes, horsed up, and allowed to drain. 
The reactions taking place in this process are represented in 
the following equation : 

Na2Cr207-f-2HCl=2NaCl+2Cr03+H 2 

The C1-O3 produced forms a compound with the gelatine. 
The sodium thiosulphate now acts as a reducing agent upon 
the chromic oxide, converting it from the acid to the basic 
condition, the reaction taking place in two stages. The basic 
chromium chloride held by the fiber is probably converted 
largely to Cr 2 (OH) G by the action of the sodium bicarbonate 
used in washing. 

One-bath chrome process. — In this process the skins or 
hides, after coming from the puer, are washed with running 
water and run in a pickle for about 1 hour. The pickle is 
made by dissolving 8 lb. of salt and 2 lb. aluminum sulphate 
in a small quantity of water, adding 1 lb. of sulphuric acid, 
and making up to a density of 40° bk. The object of this 
treatment is to neutralize any remaining alkalinity of the 
puer or lime, and to ensure the stock being in an acid condi- 
tion before it enters the tan. 

One-bath chrome liquor is made in many ways. A good 
solution may be made by dissolving 10 lb. of sodium dichrom- 
ate in 10 gallons of water, adding 6 lb. of syrup glucose (40° 
Be.), and then slowly introducing 10 lb. of concentrated sul- 
phuric acid. A wooden vessel should be used for making up 
this liquor. A less violent action, however, is produced by 
adding the glucose last, but in this case stoneware or other 
acid-resisting vessels must be employed A liquor, when pre- 



160 PRACTICAL TANNING 

pared as above and diluted to 45° Be., will give a product of 
such strength that 15 lb. will be required for each 100 lb. of 
pickled skins treated. 

In using this method, the necessary amount of reduced 
liquor (15 per cent of above liquor, equivalent to 4 per cent 
of dichromate) is dissolved in a sufficient quantity of water 
for proper handling of the stock, and 5 per cent of sodium 
sulphate added to the solution. The pickled skins are placed 
in the drum, the door is closed, and one-third of the solution 
introduced while the drum is in motion. At the end of 15 
minutes another third is added, and in 30 minutes the re- 
mainder. A half-hour after the last portion has been put 
in, -J per cent of sodium bicarbonate in solution is added, 
and the stock run for 15 minutes longer, or until tanned. The 
hides or skins are then removed from the drum, horsed up 
over night, neutralized with 4 per cent of sodium bicarbonate, 
thoroughly washed, horsed up again, and allowed to drain. 

The reactions taking place in the above liquor are as fol- 
lows: 

1. Na2Cr207+H 2 S04=Na 2 S04+H2Cr 2 7 

2. H 2 Cr 2 7 +H 2 0=2Cr0 3 +2H 2 

3. 2Cr0 3 +6H (reducing agent) =Cr 2 ( OH) 6 

4. Cr 2 (OH) 6 +2H 2 S04=CR 2 (OH) 2 (S0 4 ) 2 +2H 2 

The basic chromium sulphate thus formed is the tanning 
agent, and is decomposed by the hide substance into Cr 2 
(OH) 6 and Cr 2 (OH) 4 SC>4 with the liberation of free sul- 
phuric acid. This free acid must be neutralized with some 
mild alkali such as borax or sodium bicarbonate to complete 
the tannage, otherwise a reverse action is likely to take place. 

The resulting tannage is the same whether a one or two- 
bath method be employed. 

Chrome tannage by either of the processes given above may 
also be carried out in the paddle, but in this case the time of 
treatment is somewhat longer. The advantage of the paddle 
tannage is that a smoother grain is obtained with less danger 
of "pipey" leather. 



CHROME TANNAGE 161 

To understand the process of chrome tanning better we will 
take up its application to the various grades of stock: 

Glazed kid manufacture. — As previously shown, goat- 
skins come to the tanner from many different countries, where 
they are cured, in many various ways, such as sun-dried, dry- 
salted, wet-salted, clay cured, etc. The first duty in prepar- 
ing these skins for manufacture is to classify them and cure 
into different sizes and weights, namely, "bulls," "heavies," 
"large," "regulars," and "kids" ; and for quality into "firsts," 
"seconds," and "culls." 

The selected skins then pass to the first manufacturing 
process, which is called "soaking," where the skins are placed 
in tanks of fresh water for about 24 hours to become thor- 
oughly soaked for the milling process. The skins are then 
placed in large revolving drums with protruding wooden pins 
inside, and milled in running water for several hours to beat 
up and soften the skin to bring it as near as possible to the 
condition of a green skin, as it was when taken from the 
animal. 

The skins are then trimmed to remove what is termed the 
false weight, such as heads, shanks, and rough edges, which 
cannot be worked into leather. Then they pass to the liming 
process, where they are allowed to remain for 12 to 14 days. 

On being removed from the lime liquor, the skins are un- 
haired by machines, and then thrown into wash-reels with 
running water to wash out the lime, leaving a clean, solid pelt. 
They then pass through a machine to clean off the superfluous 
flesh and fat which is not a part of the skin substance from 
the flesh side of the skins. Then they are subjected to the de- 
pleting process, called "puering," to render them free from 
any trace of lime, and to make them soft and open for the 
proper action of the tanning agents. 

After puering, the skins are again thoroughly washed in 
"twisters" in warm running water. These twisters are large, 
square, perforated boxes, mounted to revolve on their opposite 
corners, which gives a twisting motion to the skins as they are 
thrown from one side to the other. The beam-house work 



162 PRACTICAL TANNING 

has now been done. The dry, hard skin has become a clean 
pelt, free from hair and dirt, with flesh and fat removed, and 
is soft and open for tanning. 

Most glazed kid is tanned by the two-bath chrome process. 




Figure 61. — Tan-room in a goatskin tannery. The operation is carried 
out either in paddle or drum as shown. 

The first bath is a solution of sodium dichromate and hydro- 
chloric acid ; the second bath is a solution of sodium hypo- 
sulphite and hydrochloric acid. Both of these processes are 
performed in what are called reels as shown in figure 61, made 
similar in shape to a half drum, but on the inside a paddle 
is mounted, which engages the liquor within the reel, and 
keeps the liquor and skins in motion. Great care is taken to 
have the exact proportions of the chemicals to the quantity 
of water, and the weight of skins to each reel. When these 
operations are finished, the product is a perfectly tanned 
leather, insoluble, and unaffected by boiling. 

After being taken from the tan liquor, the skins pass 
through what is called a "striking-out machine," to expel the 



CHROME TANNAGE 



163 



excess tan liquor so that they can be easily handled in the 
next process, which is called shaving. This work is also done 
by machine, (figures 62 and 63), and consists in cutting down 
the heavy parts of the skin to give a uniform thickness. The 




Figure 62. — Line of shaving machines used for producing a smooth 
effect on the flesh side. 



skins are now at a point where it is decided into what color 
they are to be finished, and they are sorted accordingly. The 
finest-textured and finest-grained skins are selected for browns 
and other colors, and the remainder are held for black stock. 
In many factories only black glazed kid is made, in which case 
this selection is unnecessary. 

Two-bath chrome on pickled sheepskins. — 1. The bated 
or pickled stock is weighed and placed in the mill, the door 
closed, and the following solution prepared, estimated on the 
weight of the stock: 

Chemicals Per cent 

Sodium dichromate 6 

Salt 4 

Hydrochloric acid 3 

Water, 5 times the weight of the stock. 



164 



PRACTICAL TANNING 



The mill being in motion, this solution is introduced through 
the trunnion, and the stock turned for 1| hours, or until 
struck through. The skins are removed from the drum and 
horsed-up over night to allow for draining and fixation of 
the chrome. 

Sodium thiosulphate bath. — On the following morning the 





*mmm?m 










■ ' ' •^.^■■t 




W i 


B'P>jf, 


>£ .^^Kpra 




(L*gj|g^ .JjSffi. 




9 


lip i 






V«i 


I 






\ 






'. 





Figure 63. — Shaving machine. 

skins are removed from the horse one at a time, dipped in a 
10 per cent solution of sodium bisulphite, and thrown into 
the drum. The following solution, 



Chemicals Per cent 

Sodium thiosulphate (hypo) 12 

Salt 3 

Hydrochloric acid 6 

Water, 5 times the weight of the stock. 

is added through the trunnion while the mill is in motion and 
run for 1| hours, or until a robin's-egg blue color shows. 
The skins are again horsed-up over night. 

Neutralizing. — The skins, after standing over night, are 
returned to the mill and run for a half-hour with -J per cent 
sodium bicarbonate and water equal to 5 times the weight of 
the stock. The plugs are now drawn, and the stock is washed 



CHROME TANNAGE 165 

for a half-hour with running water. The skins are then set 
out and shaved. 

2. The bated or pickled stock, having been weighed, is 
placed in the drum and the following solution prepared : 

Chemicals Per cent 

Sodium dichromate 6 

Sulphuric acid 2 

Salt 4 

with the necessary amount of water to give proper working 
conditions. The skins being on the shelf, the solution is 
placed in the bottom of the drum, the door is closed, and the 
drum is started. The turning is continued for about 1^ hours, 
or until the stock has become struck through. It is then 
horsed-up over night and allowed to drain. The next morn- 
ing the skins are returned to the drum with a solution of 6 
per cent sodium bisulphite, mixed with sufficient water to 
float the stock. They are treated in this' reducing solution for 
about an hour, or until a robin's-egg blue color shows. The 
stock is again horsed or piled for 24 hours, to allow hydration 
to take place. To neutralize the excess of acid, run the stock 
with ^ per cent of sodium bicarbonate, and finally wash well 
with running water. 

Tanolin. — The pickled stock is placed in a drum with 6 lb. 
of salt and 8 gallons of water for 100 lb. of stock and 
drummed 15 minutes. Six pounds of "tanolin," dissolved in 2 
gallons of boiling water, is the tanning material used, and it 
is divided into three parts. One part is poured into the drum, 
and the stock run for 30 minutes ; the second part is then 
added, and the machine run 30 minutes; then the last part is 
added and the drum is run an hour. Eight ounces of bicar- 
bonate of soda is dissolved in a little water and poured into 
the drum, and an hour later another 6 oz. is dissolved and 
added and the skins are drummed another hour. They should 
then be completely tanned. When removed from the drum, the 
skins should be horsed-up and allowed to drain 24 hours. They 
are then washed and neutralized. 



166 PRACTICAL TANNING 

One-bath chrome on pickled sheepskins. — This consists 
of first tanning them with aluminum sulphate and salt and 
then tanning with chrome liquor. When this process is used 
it is necessary to remove the acid from the skins. This is 
done by stirring them for a few minutes in a warm drench 
of sour bran and salt or bicarbonate of soda and salt. They 
are then in condition to receive the sulphate and salt. 

The usual formula for the preliminary tanning is 3 lb. of 
aluminum sulphate and 6 lb. of salt for 100 lb. of skins. 
These materials are dissolved in 6 gallons of warm water and 
the skins are drummed in it 30 minutes. The sulphate does 
not act as a tanning agent in this process, as it is washed out 
before the leather is dried. It serves to plump the skins and 
prevent contraction of the grain and fibers by the astringent 
chrome liquor. After the skins have been drummed with the 
sulphate and salt, 3 gallons of concentrated chrome liquor, 
diluted with 3 gallons of warm water, are poured into the 
drum in portions of 2 gallons at intervals of 30 minutes, and 
the drum is run for 2 or 3 hours or until the skins are tanned 
through. They should then be left in the liquor over night 
so that the chrome salts may take full effect on the fibers. The 
next day the tanned leather is washed and shaved .in the usual 
manner. 

Pickled sheepskins- may be tanned into plump, well-tanned 
leather in the following manner: Dissolve 3 lb. of aluminum 
sulphate and 3 lb. of salt in a few gallons of boiling water, 
and add enough cold water to make 10 gallons of solution. 
To this add slowly 8 oz. of bicarbonate of soda dissolved in 
a little hot water. Drum the skins with this liquor one hour, 
then hang them up to dry. When they are dry, wet them back 
and tan them with one-bath chrome liquor in the usual man- 
ner. The tannage is complete when a piece of chrome leather 
remains soft in boiling water; imperfectly tanned leather 
hardens and curls in boiling water. 

Process for glove leather. — The following method of han- 
dling pickled sheepskins for glove leather, although called a 
two-bath process, is really a three-bath process. The skins 



CHROME TANNAGE 167 

are not taken from the drum until they are fully tanned, when 
they finish out into soft, durable leather. 

The pickled skins are given a fairly strong re-pickle so 
that the grease will run well, and are pressed or wrung until 
as much of the natural grease as possible has been extracted. 
They should then be drummed in a salt solution until well 
broken up. Care should be taken, after the skins have started 
in the press, to keep the pressure steadily increasing. They 
are horsed-up from the salt solution and allowed to drain be- 
fore weighing. The skins are next weighed and thrown into 
a drum, and 1 per cent of salt is put on them, and 3| to 4 
per cent sodium dichromate is dissolved in 10 gallons of water 
for 100 lb. pickled weight. This should be fed in two parts. 
The skins are drummed in this from two to three hours. This 
will be a short liquor, but for the leather desired it works well. 

The next step is to put 3| per cent sulphuric acid in 10 gal- 
lons of water for each 100 lb. of skins, and 4 lb. of salt for 
2 lb. of acid. This is fed through the gudgeon and the skins 
are drummed with it for 20 minutes. Then 12 lb. of sodium 
hyposulphite are dissolved in 12 gallons of water for 100 lb. 
of stock, and the solution is fed to the skins and drummed for 
2 hours; this completes the tannage. 

The leather, after it has been horsed-up 12 hours, is washed, 
neutralized, and then fat-liquored. If it is to be finished in 
the pearl or regular chrome color it should be given 2\ per 
cent white chip soap boiled and made up to 10 gallons for 100 
lb. of leather, and drummed 20 minutes, and then given 5 
per cent of egg-yolk. Horse-up and allow to drain 24 hours, 
and hang up to dry in a moderate temperature; then drum 
the leather in warm water until it is thoroughly wet through, 
set it out, and hang it up again. Finishing is done by staking 
on the machine, dry drumming with talc, and staking again. 

If it is desired to make colors, the fat-liquoring would neces- 
sarily have to be done without the soap, and the skins would 
be colored with suitable dyestuff and handled in the finishing 
as regular chrome leather. 

Neutralizing and washing chrome sheepskins. — In every 



168 PRACTICAL TANNING 

case of chrome tannage it is necessary to drain the leather 
over horses or on smooth piles for 12 to 24 hours before pro- 
ceeding to wash and neutralize it. . This is done to allow the 
chromium hydroxide to become dehydrated and fixed in the 
fibers. 

The most efficient neutralizing substance for chrome leather 
is bicarbonate of soda. From 1 to 3 lb. is used for 100 lb. of 
leather. It is dissolved in 10 gallons of warm water, and the 
leather is run in the solution 30 minutes. The plugs are next 
pulled out and the leather is washed another half-hour with 
running water; it is then set out, or pressed and shaved. Some 
tanners shave their leather before they neutralize it. Borax is 
also often used for neutralizing skins. Less is used, but in the 
same manner as soda. 

White chrome-tanned sheepskins. — For some purposes, 
such as suspender trimmings, baseball covers, linings, etc., 
a soft white leather is required. The alum tannage can be 
used, but there are also special tannages which produce such 
leather. It is also practicable to take chrome-tanned skins, 
and by a treatment with flour and bleaching with borax and 
acid, finish them into soft, white leather. The tannage is the 
same as for any other chrome leather. After the leather is 
fully tanned it is washed and bleached. For each 100 lb. of 
skins, use 1 lb. of borax or bleaching soda dissolved in hot 
water, and wash the skins 20 minutes. Then drain out the 
water, replace the plug, and put cold water to which some 
sulphuric acid has been added into the drum, and run the 
leather with it 30 minutes. The borax opens and softens the 
skins and prevents the acids from doing injury. After the 
leather has been washed in the acid solution it should be 
washed in clean warm water, and then. shaved. The next proc- 
ess is the treatment with flour, 50 lb. being used for 100 large 
skins or 200 small ones. The flour is stirred into 10 or 12 gal- 
lons of water for 100 lb. of skins, and the leather is drummed 
in the liquor 2 hours ; it is then struck out, pressed, and given 
some fat-liquor. For some purposes the skins work out suffi- 
ciently white without th£ borax and acid treatment. Sulphon- 



CHROME TANNAGE 169 

ated oil dissolved in warm water is excellent fat-liquor for 
these skins. 

When the leather is dry it is moistened and staked, then 
run in a clean, dry drum with powdered chalk or soapstone 
for one hour and then arm-staked. Chrome skins in the nat- 
ural greenish-blue color of the process are obtained by simply 
washing, shaving, and fat-liquoring them; then drying, stak- 
ing, and tacking on boards. 

Tanning in a paddle-vat. — Where the skins are tanned in 
a paddle-vat the procedure is as follows : The first bath con- 
sists of 6 per cent of the weight of the skins of potassium or 
sodium dichromate and 3 per cent of 20° Be. muriatic acid. 
The chrome is dissolved in boiling water and added to the 
water in the wheel, about 65 gallons for 100 lb. of skins. The 
skins are paddled in the liquor for several hours and left in 
over night. The next morning they are taken out, struck-out, 
and dipped in a solution of sodium hyposulphite to which a 
little muriatic acid has been added. After dipping, the stock 
is thrown over a horse and allowed to remain for a short time 
before it is placed in the second bath. This bath consists of 
18 lb. of hypo and 5 lb. of muriatic acid in 65 gallons of water 
for 100 lb. of skins. The hypo is dissolved and added to the 
water; the acid is then poured in and the stock thrown in as 
quickly as possible. Some tanners do not add all of the acid 
at once, two-thirds being added first, and the remainder after 
the skins have been thrown in. When the yellow color of the 
stock has turned to light blue throughout the thickest skins 
the treatment is finished. The skins are taken out, placed 
over horses for 24 hours, and are then washed and neutralized. 
Both potassium dichromate and" sodium hyposulphite are used 
in excess, but without injury to the stock, a few pounds more 
or less for a large pack of skins making no difference in the 
quality of the leather. 

Process of alum and ctyrome tanning. — Skins tanned by the 
following process work out into a leather which possesses 
the qualities of both alum and chrome leather. In appearance, 
plumpness, fine grain, and feel, the leather resembles alum 



170 PRACTICAL TANNING 

leather, and chrome leather in softness and durability. The 
first step consists of tawing the skins in a solution of alum- 
inum sulphate and salt. In the second step the sulphate is 
fixed on the fibers of the skins by means of a solution of so- 
dium hyposulphite, and after this has been done another solu- 
tion of sulphate and salt is given to the skins, by means of 
which they are plumped and the thinness that follows the use 
of hyposulphite is overcome. By these operations the skins 
are thoroughly alum-tawed, and, if desired, may be finished 
without further tanning. To complete the process and pro- 
duce chrome leather, the skins after the final application of 
sulphate and salt, are chrome-tanned. In practice the process 
is as follows : 

The skins, after drenching and washing, are drained and 
weighed. For every 100 lb. a solution is prepared consisting 
of 3 lb. of aluminum sulphate and 6 lb. of salt in 3 gallons of 
water, boiled, and allowed to cool. The skins are drummed 
in this solution for 20 minutes. Then 10 lb. of hyposulphite 
are dissolved in 3 gallons of water, and this liquor is poured 
into the machine and the drumming continued for 15 minutes. 
To finish the first part of the process, a third solution is pre- 
pared by dissolving 2 lb. of aluminum sulphate and 3 lb. of salt 
in 3 gallons of water. This solution is added to the contents 
of the drum, which is run 30 minutes. 

The skins, now plump and full, are next rinsed off in clear 
water, drained several hours, and then given the chrome liquor, 
which is used without the addition of water or acid. From 
3 to 6 gallons of the concentrated chrome liquor is required 
for 100 lb. of skins. The chrome liquor is prepared as fol- 
lows : 5 or 6 lb. of chrome-alum is dissolved in 5 gallons of 
water without the aid of heat. To this solution is added from 
2\ to 3 lb. of sodium sulphate and from 12 to 16 oz. of po- 
tassium or sodium acetate, or its chemical equivalent. In a 
liquor thus prepared, the skins are drummed one hour, or until 
they are chrome-tanned. They are then allowed to drain 24 
hours, washed in the usual manner, shaved and colored. For 
thick, heavy skins, the quantity of chrome liquor used may 



CHROME TANNAGE 171 

be increased to 6 or 7 gallons for 100 lb. of stock. No free 
acids whatever are used in this process. Free acid in the 
solution, added as an element — that is, other than as produced 
by decomposition of the chemicals — will retard, if not pre- 
vent, the reaction necessary to produce leather. For this rea- 
son the skins must be perfectly neutral when treatment begins. 

After the tanning is completed, the skins should be left 
in the liquor several hours, then thrown over horses to drain 
for 24 hours, to allow for complete tannage of the fibers. The 
leather is then washed in warm borax water, then in clean 
water, and then shaved, colored, and finished. This process 
was patented by George W. Adler of Philadelphia, Penn- 
sylvania. 

New two-bath process of chrome tanning. — This process 
is similar in manipulation to the regular two-bath process. It 
can be worked by a two-bath or one-bath method. 

The directions for one-bath are as follows: For 100 lb. of 
skins use 4 lb. of sodium dichromate and 3 lb. of 20° Be. 
muriatic acid and sufficient water for the pack of skins to be 
processed properly. When the skins are thoroughly impreg- 
nated with this liquor and seasoned, add to the bath, while the 
goods are in motion, 20 per cent of the weight of the skins of 
"S. Z." solution* and 35 per cent of "S. K." solution," these 
two solutions being mixed before they are added to the bath. 
Then add, the skins being in motion, 5 per cent of 66° Be. 
sulphuric acid ; but before adding the acid, mix it with about 
30 times or more its weight of water. Then add this mix- 
ture through a lead-lined wooden funnel, long enough to reach 

a Use 80 lb. of sodium nitrate and 84 lb. of hot water. 

b Use 48 lb. of fresh chloride of lime, 48 lb. of soda ash, and 384 lb. of hot water. 
Dissolve the soda ash in hot water. When all is dissolved, add the chloride of lime 
through a sieve, keeping the liquor always well stirred. When all the lime is stirred 
in, let the liquor settle until it becomes clear — say in two days — then draw off 
the clear liquor for use as above, and throw the sediment away. 

Both S. Z. and S. K. liquors may be kept in one vessel — -carboy, vat, or hogshead — 
provided the proportions are maintained, and when wanted, the proper quantity is 
taken out. A wooden tank or hogshead should be 'ised for making the solution. 

In place of S. K» and S. Z. solutions, sodium peroxide and sulphuric acid may be 
used. To each 100 gallons of water in the vat add 5 lb. and 5 oz. of 62° Be. 
sulphuric acid, and stir well; then sift a little at a time 4 lb. of sodium peroxide, 
while stirring well; use lukewarm water for the bath. When this bath is ready, put 
the previously chromed skins into it, and paddle them until they are tanned. 



172 PRACTICAL TANNING 

to the bottom of the vat, and placed at one corner of it, while 
the goods are in motion. 

The skins are finished after about 1^ days. No damage will 
result should they remain longer in the liquor. When done, 
wash and finish them. This tannage produces a finer grain, 
less contracted, and besides, sulphur as in the hypo process, 
is not present. Skins treated by this tannage are best for mak- 
ing enamel or patent-finish leather. 

Neutralising and washing the tanned leather. — The object 
of these processes is to remove the acid and salts from the 
leather and make it perfectly neutral for coloring, fat-liquor- 
ing, and finishing. Chrome-tanned leather is unique in one 
respect: that is, it will stand any amount of washing with 
water without injury. Water alone, however, removes the 
acid so slowly that it is common practice for tanners to add 
a small quantity of alkali to expedite the work. 

In all cases of chrome tanning, whether by the two-bath or 
the one-bath method, the leather should press and drain from 
12 to 24 hours to allow the chromium hydroxide to become 
dehydrated and fixed in the fibers. It is then in the proper 
condition to be washed and neutralized. 

The use of sodium bicarbonate for neutralizing the leather 
is recommended. It destroys the free acid, helps to fix the 
chrome, is inexpensive, and does no damage to the leather. 
An excess of the soda is used in enough water to wash well in 
a drum. This excess does no harm to the leather. The leather 
is washed 30 minutes, when the plugs are pulled out and the 
leather is washed half an hour longer with running water. 
The skins are then struck out and shaved. 

Neutralizing with borax. — A common method of removing 
the acid from the leather involves the use of borax, the quan- 
tity required varying with the amount of acid present in the 
leather ; but it should be remembered that only as much should 
be used as to have the leather still show a very weak acid re- 
action. As a rule, from 1 to 2 per cent of borax, calculated 
on the shaver's weight of the leather, is sufficient. The borax 
is dissolved in hot water and added to the water in which the 



CHROME TANNAGE 173 

leather is washed. The leather is drummed in this water for 
40 minutes at a temperature of 80° F. After it has been thus 
neutralized, it is better to wash it well with running water. 

Insufficient neutralization of the leather, which is indicated 
by blue litmus paper turning red when pressed against the 
leather in the cut, may cause various difficulties. It may es- 
pecially cause an unsatisfactory absorption of the fat-liquor, 
or lead to the dyestuff being fixed too surficially (merely on 
the surface; little penetration), or precipitated in the bath; 
besides, leather insufficiently neutralized has a tendency to 
spew. Some tanners shave their leather before they neutral- 
ize it; others neutralize before shaving. In some tanneries 
the leather is first washed in warm running water. The borax 
is then dissolved in sufficient water to allow the leather to move, 
freely in the drum, and the treatment in such water, prefer- 
ably warm, should continue 30 minutes. The leather is then 
rinsed well in warm water. Where the skins are shaved be- 
fore they are neutralized and washed, and are fat-liquored or 
dyed immediately afterwards, me last rinsing should be in 
water at 125° F., thus raising the temperature of the skins in 
anticipation of the coloring or fat-liquoring process which 

follows. 

Notes and suggestions. — It is not always practicable for 
the tanner to follow set formulas and rules in chrome tanning, 
on account of the difference in the raw stock he uses. The 
skins should be given what they require and no more. In the 
second or hypo bath it is best to add only about two-thirds of 
the acid to the hypo solution, then, as the process proceeds, 
add more acid until the prescribed quantity has been used. 
The skins should come from the second bath as nearly neutral 
as possible, and operations should be conducted to attain this 
result. More chemicals than necessary are generally used, 
and more than the skins take up. Experience has proved this to 
be good practice, especially where a paddle-vat is used. The 
liquors are never fully exhausted when the skins are taken 
out, yet it is best to run them out and prepare new liquors for 
the next pack of skins. It is best to let the goods drain over 



174. PRACTICAL TANNING 

night from the first bath, and strike them out before putting 
them into the second bath. When a two-bath process is used, 
there is no danger of contracted grain, and the leather works 
out soft and silky and to the greatest possible area of meas- 
urement. Skins pickled with aluminum sulphate and salt can 
be tanned without being de-pickled; but if considered advis- 
able to remove acid pickle, it can be done in a bath of whit- 
ing (chalk) and salt, the skins being then washed in warm salt 
water and tanned; but bicarbonate of soda is to be preferred 
to whiting, as the latter produces calcium sulphate with slight 
solubility. 

It is feasible in using the two-bath process of chrome tan- 
ning to pickle the skins with muriatic acid and salt, and then 
give them the first bath, which is made of potassium or sodium 
dichromate and salt without acid. When this is done, the 
acid pickle serves to liberate the chromic acid in the bath. 
Whenever pickled skins are being tanned, considerable salt 
should be added to the first liquor. The first or chrome bath 
is given most advantageously in a drum; the second or re- 
ducing bath may be applied in either a drum or a paddle-vat. 
There should always be sufficient water used to give proper 
working conditions. The ratio of potash or soda to the weight 
of the skins may vary considerably without affecting the result. 

Some tanners put the skins into the solution of sodium 
hyposulphite and then add the acid rather slowly. Others 
add all the acid to the hypo-bath, and as soon as the liquor 
turns milky, throw the skins in as rapidly as possible. It is the 
opinion of the author that the latter method is the better of 
the two. When the tannage seems to be finished, it is advis- 
able to leave the leather in the liquor several hours or over 
night, to ensure complete reduction and deposition of the basic 
chrome salt. The quantity of sodium hyposulphite may range 
from 10 to 20 lb. for 100 lb. of skins, but.it is the general rule 
to use more than the stock requires, as an excess does no harm, 
it being rather beneficial to the quality of the leather. It is 
advisable to dip the chromed skins into a fairly strong solu- 
tion of hypo before putting them into the second bath. This 



CHROME TANNAGE 175 

dip may consist of 5 lb. of hypo in 10 gallons of water, or 
a 10 per cent solution of sodium bisulphite. This prevents 
"bleeding" of the chrome into the second bath, and drawn 
grain. Sodium hyposulphite is used with acid; in the second 
liquor, sodium bisulphite without acid. 

Difference between one-bath and two-bath chrome- 
tanned leathers. — One of the main causes of the differences 
between leather tanned by the one-bath method and that 
tanned by the two-bath method, says the "Shoe and Leather 
Reporter," is to be found in the fact that free sulphur is de- 
posited on the fibers of the skins by the two-bath when hypo 
is used for reducing, and not in the one-bath process. In both 
processes, the chrome salt which actually converts the pelt 
into leather is a basic one, so that the main difference is not 
to be sought in the nature of the actual tannage, but rather 
in some of the side reactions. One of these reactions in the 
two-bath process, but not in the single-bath, is the liberation 
of sulphur when sodium hyposulphite and muriatic acid are 
used in the second bath. It is customary to add the acid, to the 
solution of hypo until a slight turbidity or milkiness appears, 
before introducing the skins. The sulphur dioxide takes part 
in the reduction of the chromic acid in the skins, and the free 
sulphur is precipitated both in the surrounding liquor and in 
the fibers of the goods. It is the free sulphur that produces 
the turbidity of the liquor. This sulphur produces softness, 
gives the leather its white appearance, and acts as a kind of a 
lubricant to the fibers, so that they slip over one another more 
readily, producing the effect of softness or mellowness. 

Free sulphur can be incorporated into leather tanned by the 
one-bath process by a -special operation proposed by Eitner, 
the German leather chemist. This operation consists of treat- 
ing the skins, before tanning, with sodium hyposulphite and 
acid. The goods are treated first with one, and then with the 
other, 100 lb. of pelt being drummed for 45 minutes with 100 
gallons of water, 20 lb. of salt and 4 lb. of muriatic acid. 
The goods, after drumming, are allowed to drain, and are 
again treated for 6 hours with 20 per cent hypo. The same 



176 PRACTICAL TANNING 

reaction takes place as that described for the two-bath process, 
the acid liberating the sulphur from the hypo, but in this case 
the precipitation of the sulphur takes place entirely in and on 
the fibers. Skins treated by this process, and then tanned by 
the one-bath method, have most of the properties of two- 
tanned leather. 

A simple test to prove whether leather has been tanned by 
the one-bath or the two-bath process, consists in determining 
whether there is any free sulphur in it. A silver coin is 
cleaned and moistened, and then wrapped round with a piece 
of the leather and put in a warm place. In the case of heavy 
leather a slit should be made with a knife, and the coin placed 
in it. After an hour or so, if there is free sulphur in the 
leather, the coin will be found to be darkened or blackened by 
the action of the sulphur on the silver. 

Chrome-tanned side leather. — Hides that are intended for 
chrome upper leather are split out of lime, and the grains are 
washed, bated, and pickled. The processes of tanning such 
grains are the same as for the grains of acid-pickled sides. 
A fine chrome side leather is obtained by tanning the grains in 
the two-bath process described. The process can be carried 
out in a paddle-wheel as follows : 

The first or chrome bath consists of 6 per cent of the 
weight of the goods of potassium or sodium dichromate, 5 per 
cent of salt, and 3 per cent of muriatic acid. The dichromate 
is dissolved in boiling water and added to the water in the 
paddle-wheel, about 65 gallons of water being used for 100 
lb. of stock. The salt and acid are added and the liquor is 
ready. The stock is run in the first bath for several hours, 
then allowed to remain at rest over night. The next morn- 
ing the grains are removed from the wheel, struck out, and 
then dipped into a weak solution of sodium hyposulphite to 
which a little muriatic acid is added. After being dipped, the 
stock is thrown on a- horse, and allowed to remain a short 
time before it is placed in the second bath of the process. 

The second bath consists of 12 per cent of sodium hypo- 
sulphite to which 6 per cent of muriatic acid is added, in 65 



CHROME TANNAGE 177 

gallons of water for 100 lb. of stock. When the yellow color 
has disappeared and the leather is of a greenish-blue color 
throughout, the tannage is completed and the leather is al- 
lowed to drain at least 24 hours, when it is washed and 
neutralized. 

One-bath chrome process for acid-pickled stock. — The one- 
bath process of chrome tanning is generally considered safer 
and more economical than the two-bath for this class of stock. 
The tanner can prepare his chrome liquor of chrome-alum and 
soda, or of sodium, dichromate and glucose, or he can buy a 
concentrated one-bath chrome liquor and use it according to 
the instructions furnished by the manufacturer. 

Process for alumina-pickled grains. — Grains that are split 
from hides pickled with aluminum sulphate and salt may be 
tanned in the two-bath process the same as acid-pickled stock. 
They may also be tanned in the manner described for acid- 
pickled goods with one-bath chrome liquor. 

Process for unsplit sides. — Sides that are not split previous 
to tanning are tanned most satisfactorily in one-bath chrome 
liquor in a vat with paddles. They are bated, washed, and 
pickled either with acid and salt, or with aluminum sulphate 
and salt. For every 100 gallons of water in the vat, 35 lb. of 
salt are put in and dissolved. The hides are then introduced 
and the paddle run for half an hour. Concentrated chrome 
liquor is then dissolved in warm water until the solution stands 
at 50°, Be. scale. When the hides have been in the salt water 
30 minutes, 2 quarts of the chrome liquor are added and the 
paddle is run an hour. An addition of 3 quarts of the chrome 
solution is then made to the tan liquor, and the paddle is run 
3 hours. More chrome solution is then added, and the hides 
are kept in the bath until they are tanned throughout. 

The tan liquor can also be made by adding 3 gallons of the 
concentrated chrome solution to the salt water to start with, 
and then add 3 or 4 gallons more for every 100 gallons of 
water as the tanning proceeds. When fully tanned, the hides 
are taken out and pressed for splitting, milled in a dry mill 
to open them up, jacked and split as desired. The grains and 



178 PRACTICAL TANNING 

splits are next put into the drum and re-tanned by being 
drummed 10 minutes in a solution of salt and then for 2 or 
3 hours with 4 quarts of the concentrated one-bath material. 
The leather is then washed and shaved. 

Neutralising and washing. — After being tanned, the leather 
should be allowed to press and drain 24 hours before it is 
washed. The first washing is done in a drum with ^ lb. of 
bicarbonate of soda in 15 gallons of water for 100 lb. of 
leather. The drum is run a half-hour, when the plugs are 
pulled out and the leather is then washed another half-hour 
with running water. 

The neutralization can also be accomplished by using 1 lb. 
of borax in 15 gallons of water; washing in this solution 30 
minutes, then washing in running water another 30 minutes, 
and setting-out and shaving the leather. 

Chrome side glove and mitten leather. — Hides which are 
intended for glove and mitten leather should be thoroughly 
limed and bated in such manner that when tanned they are 
soft and elastic. The tanning is done most easily with one- 
bath liquor, the leather after tanning being allowed to drain 
until the next day. The stock is handled most readily when 
it is split after liming. Softer leather is made by not wash- 
ing the leather until after it has been colored, fat-liquored, 
and dried. 

Chrome-tanned sole leather. — The following method of 
manufacturing chrome sole leather is chiefly remarkable for 
its simplicity. The raw stock is first of all graded, with the 
object of securing a uniform system of treatment for every 
hide. In each pack there should be no greater variation of 
weight than 10 lb. This is a very important point, being one 
of the secrets of the successful production of this class of 
leather. 

Soaking. — Five days are allowed for this process when dry 
hides are used, and one or two days for green hides. 

Liming. — This is usually accomplished with a sulphide lime 
mixture, using a 5-day system. The hides from the limes are 
hauled into a pit of lukewarm water for 24 hours. Coming 



CHROME TANNAGE 179 

from the water pit. the hides are unhaired and fleshed by 
machine. 

De-liming. — Before scudding or fine-hairing, the goods are 
paddled in lukewarm water for 10 minutes, then cleared of 
loose flesh and fine-haired. After this operation, the weight 
of the hides is ascertained, and they are again paddled in cold 
water for a few minutes, then removed and suspended in a 
pit of cold water until the next morning. Neither acid nor 
bate is used at this stage, nothing but pure, clean water. 

Pickling. — On the following day the sides are taken to the 
pickling-wheel. For every 1200 lb. of hides, take 10 per cent 
salt and 2 per cent sulphuric acid, and put in just sufficient 
water to allow the goods to move freely in the paddle-wheel, 
running the same until by taking a knife and securing a cross- 
cut from the butt there remains a thin amber line, soft, and 
almost transparent. To get this effect, a run of one, two, or 
three hours may be necessary, depending upon the stock and 
the condition of the pickling solution. On leaving the pickle, 
the sides are spread out in a smooth pile to avoid creases, and 
allowed to remain until the next day. 

Tanning. — The sides are now tacked on sticks and suspended 
in liquors made of tanolin, chrome or other crystals of equal 
strength. This process is carried out in 5 or 6 days, the liquor 
and hides being moved periodically by means of mechanical 
rockers. The original liquor may be started on a basis of 10 
per cent of the chrome crystals dissolved in the volume of 
water contained in each vat, bringing the liquor up to about 
8° Be. The supplementary liquor for each pack is 2 per cent 
of salt on the hide weight, added the day the sides are put into 
the vat. The liquor is plunged up and the sides are suspended 
in it. On the second day, 6 per cent of tanolin is boiled in 
quantities of 35 lb., this usually being one pailful, well stirred, 
and dissolved. It may then be poured into the vat in four 
portions at intervals of half an hour, the rockers being allowed 
to run for another hour after the last portion of chrome liquor 
has been added. The goods should be tanned in 5 days. At 
the end of the fourth day a crosscut should be obtained, when, 



180 PRACTICAL TANNING 

if sufficiently tanned, the hides may receive \ per cent bicarbon- 
ate of soda, dissolved and poured on the surface of the liquor 
in the vat. If the cutting shows incomplete tannage and un- 
satisfactory color, the liquor may be made lukewarm by means 
of a steam pipe boxed inside, the steam being circulated 
through the vat while the rockers are in motion. When the 
desired temperature is obtained, the soda may be added, and 
the liquor agitated one hour. In either case, the addition of 
soda causes a foam, denoting the acidity of the liquor. It is 
seldom beneficial to heat the liquor, for although it may hasten 
the tanning process and help the color, it reduces the sub- 
stance of the finished product, and is therefore resorted to only 
in an emergency. 

The sides may now be removed from the vat and laid out in 
a pile, grain exposed to the air, for at least an hour before 
washing, this being effected in the wheel or drum. A good 
plentiful supply of clean water is needed at this stage, as it 
makes all the difference between a poorly and a cleanly fin- 
ished product. Three or four hours are usually necessary for 
each wash, when the sides are taken out and spread over a 
horse to drip for a few hours. After tacking them on frames 
without stretching, the hides are dried, and then well rolled. 
For waterproof sole leather, the leather is partly dried and then 
undergoes a process of fat-liquoring and filling. For this proc- 
ess the method is to dissolve for each 100 lb. of leather — 
squeezed or semi-dry weight — 2 lb. of white soap and 1 lb. of 
neat's foot oil in 6 gallons of water. This liquor may be used 
at 125° F., and the leather drummed in it 45 minutes. On re- 
moving from the fat-liquor, the sides may be set out on the 
table or by machine, tacked on frames and dried out. The 
filling may consist of stearine, paraffin wax, glucose, or other 
similar substances, mixed in different proportions for various 
requirements. This filling process improves the impermeabil- 
ity, tightness, and firmness of the leather. 

Other tanning processes. — There are other methods of pick- 
ling and tanning hides, for chrome sole leather. One con- 
sists of pickling with aluminum sulphate and salt, and tanning 



CHROME TANNAGE 181 

in vats; and another of pickling with sulphuric acid and salt, 
tanning in pits or rocker vats. 

The hides, after pickling, may also be tanned either in the 
paddle or mill as given under such leather. In cases of drum 
tanning, however, the stock should be run for short intervals 
only, otherwise a drawn grain may result. 

Chrome sole leather is also given weight and filling after 
it is tanned by being drummed with quebracho extract. It 
is claimed that 7 to 8 lb. of quebracho liquor, 70° bk., 
for each side of leather should be drummed into the latter 
after the chrome tanning is completed. Leather treated in 
this manner resembles vegetable-tanned sole leather in appear- 
ance, repels moisture, wears well, and can be sold by the pound 
the same as the older tannage. This combination process takes 
about 30 days from the raw hide to the finished product. A 
combination tannage may also be obtained by suspending the 
chrome-tanned hides for 10 days in a 40° bk. extract, and then 
extracting and finishing as for vegetable-tanned stock. 

Chrome-tanned harness leather. — In the handling of 
hides for chrome harness leather, the methods of de-hairing 
and bating should be such as not to deplete them, and pre- 
serve the strength of the fibers. To get heavy leather, heavy 
hides must be used, weighing from 60 to 80 lb. each, and they 
must be plump, as there is no way of plumping chrome leather. 

The hides are trimmed and hung in cold water to soak. 
After soaking 24 hours, they are split into sides, put back into 
the water, and soaked 24 hours longer; when they are fleshed 
and soaked over night in fresh water. Splitting into sides and 
fleshing may be done after the hides have soaked 48 hours; 
they are then re-soaked over night to be made as soft and 
clean as possible. 

Liming. — The sides are next toggled together in a long chain 
and put into the first lime. For this class of stock a fairly 
long liming is necessary, and a small amount of sodium sulphide 
at the start is desirable also. When the hides come from the 
limes, they are passed into clean warm water, from which, 
after 3 or 4 hours, they are unhaired on a machine. After 



182 PRACTICAL TANNING 

the hair has been removed, the hides should be washed with 
running water for 15 minutes, then put into clean warm water 
for 2 hours, after which they are fine-haired and worked on 
the grain. Thorough working-out of the grain is necessary 
to ensure clear, tough grain which will not crack. 

Bating. — This may be done with lactic acid or with any 
other suitable bate; the bacterial bates, of course, produce a 
finer-grained leather than any acid de-liming process. 

Pickling. — A paddle-vat is used for this process. To each 
100 gallons of water in the vat, 30 lb. of salt are added, and 
to this liquor, for each 100 lb. of hides, 2 lb. of sulphuric acid 
and 15 lb. of salt. For succeeding packs, 15 lb. of salt and 
1| lb. of acid are used. 

The paddle should be run for an hour, and then allowed to 
rest 2 hours, then run half an hour, and the hides left in the 
liquor over night. The next morning they are removed and 
placed in piles for 24 hours; they are then put into the tan 
liquor. 

Tanning. — A good way to tan the hides to get full flanks 
and bellies, and a fine, smooth grain, is by the use of rocker- 
vats, although paddles and even drums may also be employed. 
The same method of chrome tanning may be used as described 
under any of the one-bath processes. 

When fully tanned, the leather is put down in smooth piles 
for 48 hours. It is next washed for half an hour in water to 
which 1 lb. of borax has been added for each 100 lb. of 
leather, and then for one hour in cold running water. 

Another practical mode of tanning consists of pickling the 
hides with aluminum sulphate and salt, then drying, dampen- 
ing, and softening with warm water, and finally tanning in 
chrome liquor. This process produces well-tanned leather. 

Re-tanning. — After being tanned and washed, the leather is 
re-tanned with quebracho extract or with gambier, preferably 
the former. For each average side, from 1 to 2 lb. of solid 
quebracho extract is used. It is dissolved in boiling water, 
enough water being then added to make 15 gallons of liquor 



CHROME TANNAGE 183 

for each 100 lb. of leather. The sides are run in the liquor 
one hour, then placed in piles until the next day, when they 
are either pressed or put through a wringer. If pressed, they 
should be run in a dry mill for 15 minutes to remove the 
press marks. The leather is then shaved just enough to re- 
move the flesh and make the backs smooth and clean. When 
gambier is used, the quantity is about 4 lb. for 100 lb. of 
leather; otherwise the process is the same as with quebracho. 

Chrome-tanned belt and strap leathers. — Hides for these 
two classes of leather are treated in the beam-house in the 
same manner as those for chrome harness and sole leathers. 
For belting leather, however, they are trimmed into butts after 
liming or after bating. The butts should each be about 4-| 
feet long and 4 feet wide, though some may have a width of 
4-J feet. The bellies and heads are tanned with extract and 
are sold as offal. The butts are then tanned with chrome 
liquor in a drum or in a vat. Tanning in a drum is effected 
by pickling the butts and tanning them with one-bath chrome, 
according to the procedure outlined for chrome upper leather. 
When a vat is used, the process is the same as for harness and 
sole leathers. 

After having been tanned and washed, the butts are fat- 
liquored with soap, oil, and degras — 1 lb. of soap, 5 lb. of 
degras, and 2 lb. of neat's foot oil boiled an hour in water, to 
which 6 oz. of borax have been added, being sufficient for 
100 lb. of leather. There should be 12 gallons of fat-liquor. 
The butts are first run in a drum, together with 12 gallons of 
water at 160° F., and 4 oz. of salts of tartar (potassium car- 
bonate) for each 100 lb. of leather. The water is drained 
off and after the fat-liquor, at 140° F., has been put in, the 
leather is run in it 45 minutes. It is then placed in piles for 
24 hours, when it is taken and set out good and hard. The 
grain is oiled with cod oil, and the butts are then hung up to 
dry. The next operation is stretching, the object of this be- 
ing to get all the stretch out of the leather. The butts are 
soaked in hot water and piled down over night. The next 
day they are stretched in belt stretchers as tight as possible 



184 PRACTICAL TANNING 

and allowed to get thoroughly dry ; they are then finished and 
ready for cutting up into belts. 

Good leather is also made by fat-liquoring the butts with 
a solution of soap, drying and dampening them, and then stuff- 
ing them with degras, paraffin, and paraffin oil. Drying and 
stretching is effected in the manner that has been described. 
A satisfactory stuffing mixture is made of 4 lb. of cod oil, 2 
lb. of black degras, and 6 lb. of stearine for 100 lb. of leather. 
No soap is used with this stuffing, which is applied at 165° F. 
The butts are then dried and finished. 

The trimmings taken from chrome belts may be re-tanned 
with hemlock or oak liquor and sold as trimmings from oak 
belts. They are first drummed in hot salt solution, next given 
a light re-tan with hemlock extract, and then laid away in 
strong hemlock or oak liquor, preferably the latter, until they 
are colored throughout, when they are dried and sold. 

Strap leather. — There are numerous uses for which soft 
strap leather is suitable. The beam-house treatment and the 
tanning are the same as for chrome harness leather. When 
tanned, the leather is washed, shaved, and fat-liquored with 
4 lb. of moellen degras, 2 lb. of cod oil, 2 lb. of wool grease, 
1 lb. of soap, and 7 oz. of alkali, boiled, and made into an 
emulsion with 12 gallons of water for 100 lb. of leather. 

After the leather has been drummed in this fat-liquor 40 
minutes, the liquor is drained off, and the leather washed in 
warm water containing 1 pint of ammonia in 10 gallons of 
water. This water is drained off at the end of 10 minutes, 
and the leather is then re-tanned with gambier, 4 lb. dissolved 
in 15 gallons of water being used for 100 lb. of stock. The 
leather is drummed with this liquor for an hour; it is then 
set out on the grain and hung up to dry. Any rough spots 
can be buffed off before the leather is finished. 

The finish is made by boiling 8 oz. of Irish moss, 8 oz. of 
starch, 8 oz. of soap, and 1 pint of olive oil in 4 gallons of 
water for 30 minutes. When cool, the solution is strained and 
enough water is added to make 8 gallons of finish. The 
leather is given a coat of this finish, staked on the flesh side, 



CHROME TANNAGE 185 

rolled, and hung up to dry or tacked in frames. It should 
be rolled immediately after staking and before it is dried. 
When dry, it is given a second coat of finish, dried, and rolled 
again. This process makes tough, pliable, and durable leather 
which outwears the best bark-tanned product. 

White side leather.— A white leather which closely resem- 
bles alum leather is made by tanning the grains of split hides 
in a one-bath chrome process, and then either bleaching the 
leather with borax and sulphuric acid, or treating it with flour, 
or both. The hides should be split out of lime; the grains are 
then bated and pickled with sulphuric acid and salt. When 
the leather is tanned, wash it in a fairly hot 2 per cent solu- 
tion of borax for a half-hour. Then prepare a solution of 
sulphuric acid and water, made by adding acid to water until 
the solution is 1 per cent in strength. Take the leather from 
the borax bath and wash it in a drum in the acid bath; then 
wash it in clear water to remove the acid; next fat-liquor it. 

Treatment with flour. — Drumming the leather with flour is 
another way to make it white. The flour treatment can be 
used alone, or after the borax and acid process. The leather 
is washed after tanning, and is then given the flour treatment, 
50 lb. of flour being sufficient for 50 to 100 sides, according 
to size. The flour should be stirred into a thin paste with 
water before it is used. The leather is drummed with the 
flour for 2 hours, and is then fat-liquored. 

Acid fat-liquor dissolved in hot water is most suitable for 
this leather, from 4 to 6 lb. of the soluble oil being sufficient 
for 100 lb. of chrome leather. It is mixed with 10 gallons 
of hot water and applied to the leather immediately after the 
flour treatment. The leather is then dried, staked, and finished. 

Finishing. — After having been staked, the leather is run in 
a closed drum, together with powdered chalk or soapstone, for 
an hour or longer; it is staked again, and then is ready for 
use. Properly tanned and fat-liquored, the leather finishes up 
soft and white, and is excellent material. 

Tanning with aluminum sulphate. — White leather which is 
suitable for various purposes is made by tanning acid-pickled 



186 PRACTICAL TANNING 

grains and flesh splits with a solution of basic aluminum sul- 
phate. Splitting is done preferably out of lime, the stock then 
being bated and pickled. 

To prepare the tan liquor, boil 12 lb. of sulphate in 10 gal- 
lons of water.; also dissolve 24 oz. of bicarbonate of soda in 
1 gallon of hot water. Pour the soda solution slowly and 
with constant stirring into the sulphate solution. When mixed, 
let the liquor cool to 80° F. before using. 

Put the pickled stock into a drum, together with 10 gallons 
of water, 1 lb. of Glauber's salt and 3 lb. of common salt for 
100 lb. of stock. Drum 20 minutes, then drain off the liquor. 
Put 10 gallons of lukewarm water and 4 lb. of salt into the 
drum, and run the sides in this brine for 10 minutes. Then 
pour half of the sulphate and soda liquor into the drum and 
run the sides in it for 3 hours. At the end of that period take 
the stock out and place it over a horse to drain until the next 
day, then hang it up to dry. When dry, put the leather back 
into the drum, together with a few pails of water, and run 
10 minutes. Then add the other half of the sulphate-soda 
liquor and drum 3 hours. Now add sufficient one-bath chrome 
liquor to give 2 per cent of dichrome on the weight of the 
stock, and mill one hour. Horse-up the leather until the next 
day, and then hang it up to dry. 

Fat-liquoring with acid fat-liquor. — When dry, let the 
leather remain in the dry condition in a clean dry room for 
two weeks; then dampen it with warm water preparatory to 
fat-liquoring. Sulphonated oil imparts the necessary softness 
to the leather without discoloring or making it greasy. For 
each 100 lb. of dry leather use 7 lb. of the oil dissolved in 
10 gallons of water at 95° F. Drum the moistened leather 
40 minutes with the solution of oil; then let it drain over 
night. The next day strike out the grain and apply a mix- 
ture of talc, 2 parts of glycerine, and 4 parts of water; then 
hang the leather up to dry. 

Finishing. — This consists simply of moistening and staking 
the leather and tacking it on boards. When dry and taken 
from the boards, if not soft enough, re-stake it; or if stak- 



CHROME TANNAGE 187 

ing does not soften it sufficiently, give it more fat-liquor ; and 
if the leather does not appear to be entirely tanned it can be re- 
turned to the drum and re-tanned with sulphate and soda 
liquor, and then dried as before. The grain may be buffed 
off if desired ; and the appearance of the flesh side can be im- 
proved by buffing, on an emery wheel. 

If it is desired to re-tan the leather into chrome stock, this 
can be done by wetting the goods back and re-tanning with 
one-bath chrome liquor, coloring, and finishing the same as 
regular chrome leather. 

Chrome velvet leather. — The chrome-tanned sides are fat- 
liquored in the usual manner, some substance being added, 
which, during the subsequent dyeing, isolates the fibers of the 
leather in such manner as to allow its being soaked and soft- 
ened without difficulty; dextrine, grape sugar, syrup, etc., are 
used for this purpose. The leather is then dried and buffed. 
In case of grain leather, either the flesh side is buffed or the 
grain is snuffed. Flesh splits are buffed on the flesh side. 
The snuffed leather is then drummed with warm water until 
it has regained its original softness, and is dyed with acid dye- 
stuffs and sodium bisulphate. During or after the dyeing, a 
somewhat larger quantity of gambier or sumac is added than 
is otherwise customary with chrome leather, in order to im- 
part the necessary firmness to the leather. The velvet is then 
raised by working the leather in the dry drum after it has 
absorbed some moisture by treatment with wet sawdust. 

Chrome-tanned patent leather. — Hides intended for 
chrome patent leather should be carefully selected after they 
have been de-haired. The grain must be as nearly perfect 
as possible. Only small pattern and plump hides can be made 
into patent leather, as large, spready, and thin hides are of 
loose texture when tanned. After the hair and fine hair have 
been removed, the hides should be washed in a wash-wheel. 
They are then bated, which must be carefully done, because 
if the hides are bated too much the leather is loose and breaks 
coarse, and if not bated enough, the grain is harsh and tender. 
A thin grain is to be preferred to a thick one. The former 



188 PRACTICAL TANNING 

has more elasticity than the latter, and is therefore less likely 
to crack. After the hides are bated they should be washed a 
few minutes in warm water to cleanse the grain. Pickling 
then follows. 

The one-bath process of tanning is to be preferred for 
patent leather, as it gives the most measurement and there is 
no sulphur to cause trouble after the leather is finished. Drum 
the grains in salt water; then give them the tanning liquor 
and continue drumming until the leather is fully tanned. The 
leather can be washed, colored, and fat-liquored in the same 
manner as other chrome leather. 

Coloring and fat -liquoring. — Coloring is best effected with 
logwood (hematin) and direct chrome leather black. Fat- 
liquoring is done most satisfactorily with degras and soap, 
or with the former alone. It is then struck out, oiled on the 
grain, and hung up to dry in a warm room. Drying should 
proceed rapidly so that the leather will dry as firm as possible. 
Ordinarily, chrome patent leather requires de-greasing before 
finishing. 

Staking and 'finishing. — When the leather has dried, it is 
dampened, staked, and tacked out as tight as possible. When 
taken from the frames, it is usually sufficiently firm to be 
finished, were it not for the grease in it, which must be re- 
moved. Some of the grease applied in fat-liquoring, and 
some of the oil applied to the grain, does not combine with 
the fibers, and unless removed, causes the varnish to slip over 
the leather, making finishing impossible. De-greasing is done 
most satisfactorily with naphtha. Where a large quantity of 
leather is being made, a naphtha plant is necessary or else 
the leather must be sent to a de-greasing establishment, and 
treated by those who make a business of extracting grease 
from leather. De-greasing can also be done by soaking the 
leather in naphtha for 10 hours, then pressing out the naph- 
tha and drying, the leather. The action of the naphtha upon 
chrome leather is harmless; and where the leather has been 
well fat-liquored and oiled, no strength is lost through the 
de-greasing operation. 



CHROME TANNAGE 189 

Sides for patent leather can be tanned with chrome liquor 
and then split to the desired substance and re-tanned. This 
improves the "break" of the grain and softness to feel. So- 
dium sulphide should be used with lime in preparing the hides 
for tanning. It gives the grain an appearance similar to colt- 
skin, removes the fine .hair, and produces fuller and plumper 
leather than lime alone or lime and red arsenic. All fine 
hair must be removed, as it is one of the worst troubles to 
contend with in making patent leather. Hides that weigh 
more than forty pounds each are not suitable for patent 
leather. 

White chrome. — On wet pickled weight, run the stock in 
a mill with 2\ per cent formaldehyde, 7\ per cent aluminum 
sulphate, 10 per cent salt, and 12 gallons of water. Add this 
in four portions at half-hour intervals, and run for 3^ hours. 
Horse-up over night. Return the stock to the drum, and add 
enough one-bath chrome liquor to give 2 per cent sodium' 
dichromate on the weight of the stock. Run for an hour and 
add \ per cent of sodium bicarbonate. Horse-up over night. 
Then neutralize and wash, and fat-liquor with 1 per cent glyc- 
erine, 5 per cent egg-yolk, and 10 per cent of flour. Dry 
and re-fat with sulphonated oil, and finally dry, sammie,. stake, 
and tack. 

Tanolin T. — Calfskins and coltskins may be tanned with 
"tanolin T" in a paddle-wheel, in the manner outlined below : 

Pickling. — Weigh the skins after washing from the bate. 

First pack. — For each 100 gallons of water in the tub dis- 
solve 40 lb. of salt. Then for each 100 lb. of skins add 1^ 
lb. of 66° Be. sulphuric acid. 

Start the paddle, throw in the skins and allow the paddle 
to turn 3 hours. Then shut down the paddle and allow the 
skins to lie in the liquor until an hour before stopping for 
the night ; then run an hour, then allow the skins to lie in the 
liquor over night. The next morning run the paddle one 
hour and then haul the skins, and either horse up, smooth or 
pile down flat for 24 to 48 hours. When hauling the skins 
from the tub, arrange it so that the surplus liquor clinging 



190 PRACTICAL TANNING 

to them may drain back into the tub before horsing-up or 
piling-down. 

Second pack. — Strengthen the liquor by adding 10 lb. of 
salt and 1| lb. of sulphuric acid for each 100 lb. of skins. 
Then proceed in the same manner as for first pack. 

Third, fourth, fifth, and sixth packs. — Strengthen the liquor 
by adding 8 lb. of salt and 1^ lb. of sulphuric acid for each 
100 lb. of skins, and proceed as for previous packs. 

Seventh, eighth, ninth, tenth, eleventh and twelfth packs. — 
Strengthen the liquor by adding 6 lb. of salt and 1 lb. of sul- 
phuric acid for each 100 lb. of skins, and proceed as for pre- 
vious packs. 

After 12 packs have been pickled, clean out the tub and 
start again. 

This formula requires that each pack must contain enough 
skins to make a full load for the size of the paddle-tub used. 
If less than a full pack is to be pickled, a drum should be 
used. 

Tanning: First pack. — For each 100 gallons of water in 
the paddle dissolve 50 lb. of salt. Then for each 100 lb. of 
skins to be tanned, dissolve 9 lb. of tanolin T, as directed 
below. 

Warm the liquor to 75 or 80° F. Start the paddle and 
throw in the pickled skins (never throw in the skins unless 
the paddle is running). 

Take half of the tanolin solution and add to the contents of 
the paddle and run for an hour; then add the other half and 
run the paddle for the remainder of the day. Two hours 
before stopping for the night, warm the liquor to 85 or 90° 
F. and add \ lb. of bicarbonate of soda or borax, dissolved 
in a little water, for each 100 lb. of skirls. Leave the skins 
in the liquor over night. On the second day run the paddle 
2 hours in the morning and 2 hours in the afternoon ; warm 
up the liquor again before stopping for the night, and again 
leave in the liquor over night. When the skins have been in 
the liquor 48 hours they should be tanned, but if any doubt 
exists run the skins until they are tanned. When completely 



CHROME TANNAGE 191 

tanned they are removed and horsed-up smooth or piled down 
flat, and allowed to drain 24 to 48 hours. 

Never start tanning in the paddle-tub unless there is suf- 
ficient time before closing for the day to run the paddle at 
least 2 hours after the last portion of the tanolin solution has 
been added. If the skins are completely tanned a piece cut 
off from the thickest part should stand boiling. If this 
shrinks materially, and becomes hard after boiling, the skins 
are not thoroughly tanned, and should be left in the tan liquor 
and run until the leather will stand boiling. Be sure that 
the skins are completely tanned. There is no danger of over- 
tanning the skins by leaving them too long in the tanolin. 

Second pack : — Strengthen the liquor by adding 8 lb. of 
salt and 9 lb. of tanolin T for each 100 lb. of skins, as directed 
for the first pack. 

Third, fourth, fifth, sixth and seventh packs: — Strengthen 
the liquor by adding 6 lb. of salt and 7 lb. of tanolin T, for 
each 100 lb. of skins, as directed for the first pack. 

Eighth, ninth and tenth packs : — Strengthen the liquor by 
adding 4 lb. of salt and 6 lb. of tanolin T for each 100 lb. of 
skins, as directed for the first pack. 

Two hours before stopping for the night of the first day, 
for each pack add to the liquor \ lb. of bicarbonate of soda, 
dissolved in a little water, for each 100 lb. of skins. 

After 10 packs have been tanned, clean out the tub and 
start again. 

Dissolving tanolin T. — Dissolve this substance in boiling 
water, using 1 gallon of water for every 3 lb. of tanolin. 
The best way to effect its solution is to put the proper amount 
of water into a barrel or tank, insert a steam pipe, and bring 
the water to the boiling point. Then add the tanolin to the 
water, stirring it constantly with a stick to ensure its being 
well wetted, and boil vigorously until it is completely dis- 
solved. This will take about 10 minutes. Allow the solution 
to stand until the temperature is reduced to 100° F. Do not 
put the tanolin in water and then let it stand before boiling 
and dissolving. 



192 PRACTICAL TANNING 

Neutralising and washing. — After draining 24 to 48 hours 
from the tan liquor, the skins are thrown into a drum with 
a solution made of 2 lb. of bicarbonate of soda or borax, in 
10 gallons of water for each 100 lb. of skins. Mill in this 
solution for 45 minutes. Then wash the leather in running 
water until neutral to the taste. The leather must be washed 
long enough to remove all acid and salt. 

To increase suppleness. — When heavy chrome leather is 
required to be soft and supple, and yet must not contain much 
grease, as, for example, for automobile tire leathers, the 
method recommended by Eitner is satisfactory. In the or- 
dinary method of chrome tanning by the two-bath process 
sulphur is deposited in both the liquor and the fibers of the 
leather, and when thus deposited in the fibers, it produces 
softness and suppleness. 

A method for increasing the amount of sulphur deposited 
in the fibers is as follows : In the first bath, for every 100 lb. 
of pelt, take 3 lb. of chrome-alum, 1 lb. of sodium bichromate, 
and 2 lb. of hydrochloric acid. In the second bath only so- 
dium hyposulphite is used to the extent of 8 lb. No acid 
is added, as there is sufficient in the goods to produce the 
desired effect. By this means the sulphur is deposited on the 
fibers, the result being a soft, supple leather. It has a green 
color, but if it is desired to make it whiter, the following 
treatment may be applied : The goods are first pickled for 
1 or 2 hours with 1 gallon for each pound of pelt in a solu- 
tion containing 20 per cent of salt and 5 per cent of sulphuric 
acid, and 4 per cent of sodium bichromate is then added. 
This constitutes the first bath; the second bath contains hypo 
only. 

Ordinary one-bath leather can be made to represent two- 
bath leather by incorporating sulphur in the fibers. Before 
the goods are tanned, they are treated alternately with hypo 
and hydrochloric acid, then tanned by the ordinary one-bath 
process. This method produces a chrome leather with a large 
amount of free sulphur, which makes it very supple. The 
process can be carried out in either order, or even repeated 



CHROME TANNAGE 193 

more than once, that is, either hypo first, followed by hydro- 
chloric acid and salt or the reverse. 

Dissolving chrome-alum. — Several substances which are 
used in the tannery have the peculiarity that while being fairly 
soluble in water, they dissolve very slowly. For example, 
chrome-alum is soluble to the extent of 1 part in 7 or 8 parts 
of water, but it dissolves very slowly. If this salt is used 
and some remains undissolved there is danger of stains or 
uneven results being produced by the contact of the solid 
particles with the skins. In this case it is better to make 
up the solution some time in advance to be sure that all the 
crystals are dissolved. When this is impossible, or where 
the solution is required immediately, it is better to adopt 
some other means than merely stirring the crystals on the 
bottom of the vessel. A better way is to suspend the chrome- 
alum in a basket, coarse bag, or some sort of strainer in the 
water, so that the crystals are in contact with the water at 
the top of the vessel. By this means the alum is much more 
quickly dissolved, because, as it dissolves, the solution falls 
away from it by gravity, thus exposing a fresh portion of 
the crystals. If the solution of chrome-alum is to be used in 
the drum, then, of course, it may be dissolved in the requisite 
quantity of water by agitation in the machine. With some 
substances that dissolve slowly it is possible to hasten the 
solution by using hot or boiling water; but in the case of 
chrome-alum, the solution thus obtained is different from that 
in cold water, the latter being of a violet color, while that in 
hot water is green. 

The two solutions differ chemically to the extent to which 
the chrome-alum is hydrolized, and theoretically, one would 
expect the violet-colored solution to produce better tanning 
results than the green one, but the tanning effects are gener- 
ally the same in both cases. In experimental cases, two sim- 
ilar packs of calfskins were tanned in the two different colored 
solutions (made basic with soda), and after being tanned, 
were neutralized, fat-liquored, dyed, and finished, but with 
no apparent difference in the result. It was therefore con- 



194 PRACTICAL TANNING 

eluded that it is not worth the time and trouble to make the 
violet-colored solution. 

Aluminum bisulphite reduction. — The modifications of 
the ordinary chrome processes of tanning are almost legion, 
particularly so in connection with the production of one-bath 
chrome liquors. For the production of the latter, there are 
two general types of method, the first involving the use of a 
chromium compound, such as chrome-alum, which is ren- 
dered basic by the addition of some alkali, such as soda. The 
modifications in this branch include the use of different alka- 
lies for rendering the salt basic, and also the use of different 
classes of chromium compounds. The most common, of 
course, is chrome-alum, of which the active constituent is 
chromium sulphate. Other chromium salts which have been 
advocated are chromium formate, chromium acetate, and 
chromium chloride. 

In the second type of method for the production of one- 
bath chrome liquors, potassium or sodium bichromate is taken, 
and reduced by some reducing material. The chief modifica- 
tion in this type of process rests in the agent which is used 
for the reduction, both organic and inorganic materials hav- 
ing been employed. Of the organic materials, probably the 
most common and the most widely used have been cane sugar, 
glucose, glycerine, and alcohol; while the inorganic materials 
include sodium bisulphite and sodium hyposulphite. 

According to a German patent taken out by M. F. Hirch, 
the reduction is carried out by means of a solution of alumi- 
num bisulphite, which, it is claimed, has the following advan- 
tages over hypo or sodium bisulphite : 

There is no deposition of free sulphur as with sodium hypo- 
sulphite, and no great evolution of heat as with sodium bisul- 
phite. The deposition of aluminum hydrate is formed in the 
skin. The reduction should be carried out without the addi- 
tion of acid. If a solution of aluminum bisulphite of about 
14° Be. be added to a 2 per cent solution of chromic acid, 
the complete reduction of the chromic acid is attained with- 
out any precipitation. If, on the other hand, a solution of 



CHROME TANNAGE 195 

one-third the above concentration be used, the reduction of 
the chromic acid is complete, but at the same time a precip- 
itation is produced in the liquor. 

The first treatment, that is, with the concentrated solution 
of bisulphite, is suitable for tannage in one bath, while the 
liquor produced by the use of the weaker bisulphite solution 
is suitable only for the tannage in two baths. The following 
is given as a practical example : The skins, de-haired, de- 
limed, and pickled as usual, are submitted to the following 
treatment: The bath consists of 5 per cent of sodium bi- 
chromate, 2\ per cent of hydrochloric acid, and 180 per cent 
of water, calculated on the weight of pelt. The goods are 
allowed to turn in this liquor for 3 or 4 hours, and are then 
placed in a pile for 12 hours. Finally they are transferred 
to the second or reducing bath. 

This bath consists of 36 parts of solution of aluminum bisul- 
phite at 14° Be., and 220 parts of water for each 100 parts 
of pelt. The goods are turned in this liquor for 4 hours, 
when the tannage should be complete, with the grain even and 
smooth. The leathers tanned by this method are more re- 
sistant than those produced by other processes, and can be 
dyed more easily and more regularly, partly because the de- 
position of sulphur is avoided and partly because the alumina 
forms a mordant which is very favorable to dyeing. 

Recovery of chrome residues. — In the two-bath method 
of chrome tanning, the first bath, which consists of an acidi- 
fied solution of potassium or sodium bichromate, is never 
fully exhausted. It has frequently been proposed to utilize 
the residual chrome in this bath by making use of a stand- 
ing bath, that is, never wholly discarding a bath, but adding 
each time a quantity of bichromate and acid sufficient to re- 
store its original strength. Unfortunately, this renewal of 
the bath is an extremely complicated matter. 

It is probably more practical with our present knowledge 
not to try to utilize this chrome again in tanning, and by so 
doing produce a poorer quality of leather, but to recover the 
chrome in some form suitable for some other purpose. 



196 PRACTICAL TANNING 

Two processes have been proposed for the recovery of 
chrome as a by-product, both of which can be worked profit- 
ably, provided proper care is taken and operations are on a 
sufficiently large scale to warrant the expenditure for 
labor. 

The first process consists of the precipitation of the chrome 
as chromate of lead or chrome yellow. There is an exten- 
sive demand for this pigment, and the particular shade is 
not of great importance so long as it is strictly uniform. 
In order to obtain uniformity, the precipitation should be 
always made under as near the same conditions as possible 
and to obtain brilliancy, the solution should be filtered before 
precipitation takes place, and some alum added as a clarify- 
ing agent. White sugar of lead (lead acetate) should be used 
for precipitation, and a filter-press is essential for collecting 
the precipitate. The product may be dried or sold in pulp 
form to manufacturers of mixed paint. The price obtained 
for the chrome yellow depends upon the care with which it 
is made, but with ordinary precaution, this working-up of 
a by-product is fairly remunerative. 

The second method of utilizing the waste chrome is to 
reduce it with sodium bisulphite or sulphurous acid gas, pre- 
cipitate with soda ash, collect the chrome hydrate so formed 
in a filter-press, wash it thoroughly, and use it in the manu- 
facture of one-bath tan liquors. This method is in many 
ways preferable to the manufacture of chrome yellow, as it 
does not involve the worry of looking for an outside market. 
Even in the profitable recovery of this chrome, the liquors 
must be analyzed, and no great excess of reducing agents or 
soda should be employed, otherwise these chemicals may be 
wasted and no real gain obtained. 

Chrome-tanned buckskin. — The skins after the final 
washing are pickled either with sulphuric acid and salt, or 
with aluminum sulphate and salt. The goods are then al- 
lowed to drain until the next day, when they are tanned in 
a one or a two-bath process. Excellent chrome buckskin is 
obtained by tanning the pickled skins in a two-bath process, 



CHROME TANNAGE 197 

and good leather may also be made with any of the one-bath 
processes. 

White chrome buckskin. — An excellent white buckskin is 
made by tanning with one-bath chrome liquor and then treat- 
ing the skins with flour. 

One-bath chrome tannages. — While a great many pre- 
scriptions have been published for one-bath chrome tannages, 
preparation of a proper one for any given purpose is still 
considered a valuable trade secret. A little consideration of 
the one-bath chrome tan liquor from the chemical point of 
view should therefore be of some interest. 

Of first importance is the source of the chromium. So- 
dium dichromate is almost universally the cheapest raw ma- 
terial. The exception is chrome hydrate, it being occasionally 
possible to obtain chromium in the form of hydrate relatively 
cheaper than in the sodium dichromate. This is so because 
in some chemical operations the dichromate is used simply 
for its oxidizing effect, and when the chromium is reduced, 
its work is done; then it is precipitated with sodium carbonate, 
washed and offered for sale as a* by-product. Only a limited 
supply, however, can be obtained from this source in the 
United States; but large quantities are secured from Euro- 
pean coal-tar dye-works. The dichromate contains almost 
exactly 50 per cent cf chromic oxide, and 100 per cent chro- 
mic oxide in this form therefore costs just double the price 
of the dichromate. As in the dichromate, the chromium is 
present in the form of chromic anhydrite and as it must be 
in the reduced or chromic oxide form, for use in one-bath 
liquors, there has to be added to the cost of the dichromate 
that of the acid required to set free the chromic anhydrite, as 
well as that of the reducing agent used to get it into the 
chromic oxide form. For example, the cost of a liquor con- 
taining 100 lb. of chromic oxide made by reducing sodium di- 
chromate with glucose, may be figured as follows : 

200 lb. sodium dichromate at 7 cents per lb $14.00 

280 lb. sulphuric acid at $1.10 per 100 lb 2.98 

50 lb. glucose at 3 cents per lb 1.50 

Total cost of chromic oxide. $18.48 



198 PRACTICAL TANNING 

Sodium bisulphite may be used as the reducing agent in 
place of the glucose, in which case the cost shows as follows : 

200 lb. sodium dichromate at 7 cents per lb $14.00 

163 lb. sulphuric acid at $1.10 per 100 lb 1.80 

600 lb. bisulphite at 85 cents per 100 lb 5.10 

Total cost of 100 lb. of chromic oxide $20.90 

These liquors, as calculated, include the cost of the acid 
which is required to hold the chromic oxide in solution. 
If chromium hydrate is used, the cost of this acid must be 
figured; for example, the chromium hydrate is usually sold 
in the form of a 20 per cent paste, and the cost of a liquor 
containing 100 lb. chromic oxide is: 

500 lb. chromium hydrate at 31 cents per lb $17.50 

210 lb. sulphuric acid at $1.10 per 100 lb 2.31 

Total cost of 100 lb. of chromic oxide $19.81 

The cost of a liquor made of chrome-alum to contain 100 
lb. of chromic oxide is readily calculated, as this salt contains 
almost exactly 15 per cent of chromic oxide; therefore, it 
requires 667 lb. of chrome-alum at 5 cents a pound to supply 
100 lb. of chromic oxide, or a total of $33.35. 

The cost price of the materials is based on normal market 
conditions, and as the market fluctuates, new values can be 
readily substituted in the calculation given. 

Theory of chrome tanning. — The next step in this treat- 
ment is to modify the liquor so that it will produce good 
leather. This is a matter of so much importance and so 
little understood, that a great many tanners find it good busi- 
ness policy rather to pay an extra price for a liquor already 
prepared, and which has been accurately adjusted to condi- 
tions they desire, than to attempt to make a liquor of their 
own. In general, this desired modification of a tanning liquor 
is described by the rather vague term of "basicity." To un- 
derstand properly what is meant by this, we must consider 
the theory of the one-bath chrome tannage a little, that is, as 
much as it is known of it: According to present knowledge, 
salts of all descriptions, when in solution, dissociate, that is, 



CHROME TANNAGE 199 

break up into acid and basic radicals or ions, and the chemical 
properties of these ions constitute the properties of the solu- 
tion. In the case of salts of strong acids and strong bases, 
such as sodium sulphate or sodium chloride, the strong basic 
or positive character of one ion is in effect neutralized by the 
strong acid or negative power of its opposite ion, and a neutral 
solution results in a solution of such a salt. On the other 
hand, with a salt of a strong base and a weak acid, as 
sodium carbonate in solution, there is a condition in which 
the strong positive character of the sodium ion far over- 
balances the weak acid character of the carbonic ion, and 
the solution has marked basic or alkaline properties. While 
in the salts of weak bases and strong acids — such as aluminum 
and chromium sulphates — the acidic or negative character pre- 
vails, and solutions of these act in many ways as if they con- 
tained free acid. In fact, the solutions may to a certain 
extent be said to contain also free acid by the taking-on of 
water — the phenomenon known as hydrolysis — which is con- 
nected with the facts of dissociation already cited, in the 
equilibrium, as it is called, of the solution. With these theo- 
ries in mind, we can perhaps consider and explain better 
some of the observations on the behavior of the chrome tan 
liquor. An untanned hide or skin is strongly swollen or 
plumped by both acids and alkalies. The reason for this 
phenomenon has never been adequately demonstrated. Per- 
haps as good a theory as any other is that both the acid 
and alkali combine chemically with the hide fiber in such a 
way as to reduce its permeability, and thus the fibers become 
swollen by solution-pressure. Neutral salts deplete, reduce, 
or prevent any swelling of the hide. This action also has not 
been thoroughly explained, but it, too, is doubtless connected 
with the increase of osmotic or solution-pressure. 

If a chrome tanning liquor is made up of chromium sul- 
phate and nothing else in solution, it will, from the con- 
siderations above, be seen to possess strongly acid properties. 
A skin immersed in such liquor will be excessively plumped ; 
the tanning, however, will proceed very slowly, because as 



200 PRACTICAL TANNING 

treatment constitutes, the deposition of the chromic oxide will 
continually augment the acid character of the liquor, and by 
so doing the tendency of the chromic oxide to deposit will 
be retarded, until finally a condition is reached when no 
oxide at all is deposited, that is, the liquor will cease to 
tan. If to the liquor containing only chromium sulphate, 
common salt, (sodium chloride) be added, ionization will be 
prevented, the percentage of acid, however, will not be re- 
duced, but the plumping effects will be obviated. Such a 
liquor will tan with the same degree of slowness as a pure 
solution of chromium sulphate, a better leather being, how- 
ever, produced, because the excessive plumpness is prevented. 
If, in addition to the common salt, sodium carbonate be added 
to the liquor to neutralize the acid formed by the hydrolysis 
of the chromium sulphate, the third factor necessary to com- 
plete the tan liquor will be present. 

By combination with the acid, the sodium carbonate forms 
sodium sulphate, and this being a "neutral salt, will assist 
the common salt in keeping down the plumpness, at the same 
time tending to form a basic chromium sulphate. The amount 
of sodium carbonate that can be added, is, of course, strictly 
limited, because an excess will cause the precipitation of 
chromium hydroxide; and even before this point is reached, 
so much of the acid may be neutralized that the solution will 
be unstable and practically decomposed by the skin. A solu- 
tion in this condition will be found to plump as much as 
a strongly acid solution. It should perhaps be noted here 
that there is a difference between the rapidity with which solu- 
tions penetrate and the speed with which they tan. The acid 
solutions penetrate more rapidly than neutral solutions, but 
do not tan so fast; thus a skin struck through in a too acid 
solution will be found to be under-tanned. In practice, only 
the tan liquor made by the solution of the chrome hydrate 
in sulphuric acid will be found simple enough to modify as 
above described. 

The liquor made by reducing the dichromate with glu- 
cose will contain considerable sodium sulphate and some salts 



CHROME TANNAGE 201 

of organic acid, obtained from the incomplete oxidation of the 
glucose. The influence of these latter, is, however, almost 
negligible in regard to diminishing the plumping effect, but 
they do retard the tanning. As the amount of such salts varies 
according to the temperature at which the dichromate has 
been reduced, they constitute an objection to the tan liquor 
made by reduction with glucose, as they make its action 
slightly uncertain. The liquor made by the reduction with 
bisulphite is therefore slightly superior in its regularity, al- 
though a little more expensive. 

The concentration of the liquor also exerts a pronounced 
influence upon its tanning properties. In the first place, all 
the constituents of a liquor should be proportioned to each 
other, and for sure results their ratio should not be changed. 
It should be remembered that the neutral salts are a con- 
stant factor, while, on account of the chromic oxide being 
taken up by the skin, the amount of this and of the acid 
present is variable, the one constantly decreasing and the 
other constantly increasing. 

Finally, of utmost importance is the condition of the skins 
when they are put into the tan liquor. They may be acid 
or neutral, plump or depleted, but their condition should al- 
ways be the same, or allowance made for it in the tan liquor. 

Calfskin glove and mitten leathers. — Glove leather of 
durable quality is made by tanning calfskins with chrome. The 
most suitable are those which are large and thin. During 
the processes of liming, bating, and pickling prior to tanning, 
the skins are handled in the same manner as those for shoe 
leather, except that it is advisable to lime them somewhat 
more thoroughly, so that the leather will be soft and durable. 

Tanning is done by the two-bath or one-bath process in 
the manner that has been already described. Another excel- 
lent way to tan the goods is first to give an alum tannage, 
dry them out, and then re-tan with one-bath chrome liquor. 

Chrome lace leather. — Hides for lace leather are limed 
and bated in about the same manner as those for upper stock. 
A fine grain is not essential. Sodium sulphide is used in the 



202 PRACTICAL TANNING 

lime to hasten the de-hairing and give toughness to the hides. 
De-liming can be done satisfactorily with lactic acid. The 
hides are next pickled with sulphuric acid and salt, and are 
then tanned. 

Chrome lace leather is made by tanning the pickled sides 
with one-bath chrome tanning material the same as chrome 
upper leather, and then fat-liquoring and finishing in the 
following manner: The tanned and neutralized leather is 
split. The flesh splits can be finished into gusset splits, glove 
leather, or lace leather. The split lace leather is just as dur- 
able as the grain leather, but it does not look quite so good. 
The sides may be split out of lime or out of pickle, and then 
tanned with the chrome liquor. Where yellow lace leather 
is wanted, it is colored with extract of fustic and some yellow 
dye before fat-liquoring. If white leather is desired, it is 
washed in hot borax water, and next in water acidulated 
with sulphuric acid, and then thoroughly in clean water be- 
fore fat-liquoring. 

A satisfactory method of tanning chrome lace leather is 
carried out as follows : The sides are de-haired, bated, and 
washed ; they are then drummed with 2 lb. of pulverized alum 
and 4 lb. of salt for each 100 lb. of hides. The goods carry 
sufficient water from the last washing to dissolve the alum 
and salt. When they have absorbed the materials, they are 
allowed to press and drain, and, after having been partly dried, 
are split and shaved. The tanning is then completed by drum- 
ming the hides in one-bath liquor in the same manner as for 
chrome upper; they are finally washed and partly dried for 
fat-liquoring. 

The fat-liquor is made as follows : 4 oz. of potash or other 
alkali is boiled in -| gallon of water; then 2 lb. of any good 
degras and 4 lb. of tallow are added, and the whole brought 
to a quick boil. The compound requires thorough cooking. 
Then 1 quart of neat's foot oil is added, and the mixture is 
stirred until the temperature reaches a little below boiling 
point. The fat-liquor, at 150° F., is applied to the leather, 
the above quantity being used for 100 lb. 



CHROME TANNAGE 203 

When fat-liquored, the leather is struck out and oiled on 
the grain side with neat's foot oil, then stretched in frames 
until dry. After this it is moistened and staked, staking 
and drying being continued until the leather is soft and dry. 
Then it is painted on both sides with a light coat of paste 
made with tallow, starch flour, soap, and water boiled to- 
gether ; next it is dried again and finished. The chrome tan- 
nage permits the leather to be stuffed at a high temperature, 
thus ensuring thorough penetration of the stuffing grease, and 
the leather is made very elastic and durable, and peculiarly 
suitable for lace leather. Chrome lace leather does not harden, 
but remains soft and pliable until it is worn out. It does 
not burn when it goes over the pulleys. The tanning can be 
clone in any of the various methods given for chrome leather. 

Semi-chrome leather. — This class of leather, as the name 
implies, includes those leathers which are tanned partly by 
a vegetable tanning process and partly by a process of chrome 
tanning. The two processes may be carried out together, or 
consecutively, or the chrome process may be used as a re-tan- 
nage for vegetable-tanned skins. Usually the chrome process 
precedes the vegetable process, since this procedure gives the 
leather its characteristic properties. 

Among the skins that arrive in the United States in a partly 
tanned condition are sheepskins from East India, South Af- 
rica, South America, and Australia. It is these skins, par- 
ticularly those from East India, that are given the chrome 
re-tannage. The goods are sorted according to substance, 
tannage, etc., and are marked. After marking, the skins are 
equalized by splitting or shaving. The larger skins are split, 
and, if necessary, are shaved. Before splitting or shaving, 
the goods are dampened down by immersing the thick por- 
tions in warm water and finally the whole skin. Very light 
skins are dampened back by being treated with warm water 
in the drum for 10 minutes. Finally they are laid in a pile 
for a few hours to become uniformly soft and moist. 

Splitting and shaving. — In splitting, the goods should be 
left thicker than the final product is required, and then shaved 



204 PRACTICAL TANNING 

down to the required substance. The flesh splits are used for 
welting purposes, heels, linings, etc. ; the grains are de-tanned 
and then re-tanned with chrome liquor. Unless most of the 
original tannage is removed, the leather will be hard and un- 
evenly tanned. 

Stripping the tannage. — Stripping or de-tannage is accom- 
plished by means of the milder alkalies. Caustic soda should 
not be used as it is too energetic. Borax may be used with 
advantage, because it acts gently and gives a smooth grain to 
the skins. For light skins, 2 per cent, and for heavy skins, 
2\ per cent of borax is used, calculated on the weight of the 
drained goods. If washing soda is used, not more than 2 lb. 
should be taken for 100 lb. of leather. The drained skins 
are placed in the drum with warm water at 100° F., the drum 
is set in motion, and the borax or soda solution is run in 
through the hollow axle. The drum is allowed to run 30 
minutes, which is usually sufficient to remove the greater part 
of the tannin. The washing should be continued until the 
skins have a soft and slippery or semi-gelatinous feel. When 
this has been accomplished, the liquor is allowed to run out 
and warm water is run in to wash the skins. This washing 
is continued until the water coming from the drum is clear, 
showing that all dissolved tannin is removed. In order to 
neutralize the alkali retained by the leather, \ to 1 per cent 
of formic acid is added to the wash water. The progress 
of neutralization may be followed by applying a piece of blue 
litmus paper to a cut section of the skins; if the paper is 
colored a feeble red, the process is complete. A final wash- 
ing with pure water prepares the goods for the chrome re- 
tannage. 

Vegechrome. — Calf and kip skins may be tanned with 
"vegechrome" in a paddle-wheel tub by the following 
procedure : 

Pickling. — Weigh the skins after washing from the bate. 

First pack. — For each 100 gallons of water in the tub dis- 
solve 40 lb. of salt. Then for each 100 lb. of skins add 1| 
lb. of 66° Be. sulphuric acid. 



CHROME TANNAGE 205 

Start the paddle, throw in the skins, and allow the paddle 
to turn 3 hours. Then shut down the paddle and allow the 
skins to lie in the liquor until an hour before stopping for the 
night; then run one hour, and allow the skins to lie in the 
liquor over night. The next morning run the paddle one 
hour, and then haul the skins and either horse-up smooth or 
pile-down flat for 24 to 48 hours. 

Second pack. — Strengthen the liquor by adding 10 lb. of 
salt and 1| lb. of sulphuric acid for each 100 lb. of skins. 
Then proceed same as for the first pack. 

Third, fourth, fifth and sixth packs. — Strengthen the liquor 
by adding 8 lb. of salt and 1| lb. of sulphuric acid for each 
100 lb. of skins and proceed as for previous packs. 

Seventh, eighth, ninth, tenth, eleventh and twelfth packs. — 
Strengthen the liquor by adding 6 lb. of salt and 1 lb. of sul- 
phuric acid for each 100 lb. of skins and proceed as for pre- 
vious packs. 

After 12 packs have been pickled, clean out the tub and 
start again. 

This formula requires that each pack must contain enough 
skins to make a full load for the size of the paddle-tub used. 
If less than a full pack is to be pickled, a drum should be used. 

Tanning: First pack. — For each 100 gallons of water in the 
paddle-tub dissolve 50 lb. of salt. Then for each 100 lb. of 
skins to be tanned dissolve 12 lb. of vegechrome as directed 
below. 

Warm the liquor to 75 or 80° F. Start the paddle, and 
throw in the pickled skins. Never throw in the skins unless 
the paddle is running. 

Take half of this vegechrome solution and add it to the 
contents of the paddle and run for one hour; then add the 
other half and run the paddle for the remainder of the day. 
Two hours before stopping for the night, warm the liquor 
to 85 or 90° F., and add 6 oz. of bicarbonate of soda or borax, 
dissolved in a little water, for each 100 lb. of skins. Allow 
the skins to remain in the liquor over night. On the second 
day run the paddle 2 hours in the morning and 2 hours in the 



206 PRACTICAL TANNING 

afternoon; warm the liquor again before stopping for the 
night and allow the skins to lie in the liquor over night. When 
the skins have been in the liquor 48 hours, they should be 
tanned, but if any doubt exists run them until they are. 

When completely tanned, the skins are removed and horsed- 
up smooth or piled-down flat, and allowed to drain 24 to 48 
hours. 

Never start tanning in the paddle unless there is sufficient 
time before closing for the day to run it at least two hours 
after the last portion of the tanning solution has been added. 
If the skins are completely tanned, a piece cut off from the 
thickest part should stand boiling. If the piece cut off shrinks 
materially and becomes hard upon boiling, the skins are not 
thoroughly tanned and should be left in the tan liquor and 
run until the leather will stand boiling. There is no danger 
of over-tanning the skins by leaving them too long in the 
vegechrome. 

Second pack. — Strengthen the liquor by adding 8 lb. of 
salt and 12 lb. of vegechrome for each 100 lb. of skins, as 
directed for the first pack. 

Third, fourth, fifth, sixth and seventh packs. — Strengthen 
the liquor by adding 6 lb. of salt and 9| lb. of vegechrome for 
each 100 lb. of skins, as directed for the first pack. 

Eighth, ninth and tenth packs. — Strengthen the liquor by 
adding 4 lb. of salt and 8 lb. of vegechrome for each 100 lb. 
of skins, as directed for the first pack. 

Two hours before stopping for the night of the first day, 
for each pack add to the liquor 6 oz. of bicarbonate of soda, 
dissolved in a little water, for each 100 lb. of skins. 

After 10 packs have been tanned, clean out the tub and start 
again, as for the first pack. 

Dissolving vegechrome. — Dissolve the vegechrome in boil- 
ing water, using one gallon of water for every 3 lb. of vege- 
chrome. The best way to effect the solution of this material 
is to put the proper amount of water into a barrel or tank, 
insert a steam pipe, and bring the water to the boiling point. 
Then add the vegechrome to the water, stirring constantly 



CHROME TANNAGE 207 

with a stick, and boiling vigorously until it is completely dis- 
solved, which will take about 10 minutes. Allow the solution 
to stand until the temperature falls to 100° F. Do not put the 
vegechrome in water and then let it stand before boiling and 
dissolving. 

Neutralizing and washing. — After draining from the tan 
liquor the required period, the skins are then thrown into the 
drum with a solution of antimonine (antimony lactate), using 
4 oz. in 10 gallons of water not over 100° F. for each 100 
lb. of skins. Mill in this solution for a half-hour, and wash 
the skins in running water for 10 to 20 minutes. Then add 10 
gallons of water to the drum for each 100 lb. of skins, and 
in it dissolve 4 oz. of borax and run them in this borax water 
for 30 minutes. Then wash the skins in running water until 
neutral to the taste ( 1 to 3 hours, depending upon the thick- 
ness of the skins). The skins must be washed long enough 
to remove all acid and salt. 

Chrome-tanned wax calf leather. — The tanner of chrome 
calfskins finds many having defective grain which can be 
re-tanned and finished into chrome wax leather. Heavy skins 
are more- suitable for this leather than light ones, the light 
stock being more suitable for ooze leather. All skins from a 
medium up to 10 to 12 lb. can be worked into chrome wax 
leather, provided that they are free from butcher cuts on the 
flesh side. They are worked through the preliminary process 
in the same manner as those for chrome leather, being tanned 
with one-bath chrome liquor and shaved. After shaving, they 
are washed and tanned. 

Re-tanning. — This consists in re-tanning the skins with 
hemlock extract, or with a mixture of hemlock and oak ex- 
tracts, hemlock and quebracho extracts, or with other suit- 
able tanning material. Two methods of re-tanning will be 
described : 

The first liquor is a 5° bk. hemlock liquor in which the skins 
are hung 24 hours. This liquor is then strengthened to 8°, and 
the skins are left in it for 48 hours, after which the strength 
is increased to 10°, the skins remaining therein 48 hours. The 



208 P-RACTICAL TANNING 

next liquor is at 14°, and the skins are transferred to it and 
remain in it 6 days. Handle them every 2 days, or give them 
a 16° liquor for 4 days and handle every 2 days; then they 
should be given 5 days in an 18° liquor, being handled every 
other day. Re-tanning is now complete. The liquors may 
also be made up of oak and hemlock extracts in the propor- 
tion of 3 parts of the latter to 1 part of the former. Gambier 
is about the only vegetable tanning material that does not 
lose considerable of its tannin strength by precipitation in the 
presence of salt. Synthetic tans do not lose their efficiency by 
precipitation, but quebracho, hemlock, and most other vege- 
table tanning materials do. 

Re-tanning may also be done in a drum in the following 
manner: The first liquor is made of 3 lb. of hemlock extract, 
and 1 lb. of oak extract, and 5 lb. of salt in 25 gallons of 
water for 100 lb. of chrome leather. In this liquor the skins 
are run one hour, then they are piled-down for 24 hours. The 
second liquor may be the same as the first, the skins being 
run in it one hour, then piled-down for 24 hours. On 
the third day the skins are given the last re-tanning liquor, 
which is made up of 3 lb. of oak extract and 1 lb. of hemlock 
extract and no salt. The skins are run in this liquor 2 hours, 
then placed in piles for 12 hours. Re-tanning by hanging the 
goods in the liquor is doubtless the better method of the two. 
After the leather is fully re-tanned it should lie on a pile for 
48 hours, and then be fat-liquored. 

Intestinal leather. — This process makes leather from the 
intestinal membrane, which, on being bleached, has the ap- 
pearance of ordinary glove leather or kid. It is, however, 
essentially different from such leather by the absence of pores, 
thus rendering it impervious to moisture and gases, and by 
its extreme thinness coupled with great toughness or strength 
of fiber. It is distinguished from gold-beater's skin in that 
it may be sewed, the seam being firm and the leather closing 
tightly around the thread, and also by its extreme pliability 
and softness. These properties render this leather peculiarly 
suitable for the manufacture of gloves for those whose occu- 



CHROME TANNAGE 209 

pations render it necessary to protect the hands against infec- 
tious matter and poisonous solutions. The extreme softness of 
the leather permits free movement of the fingers, and its thin- 
ness gives the sense of touch full play. Unlike gold-beater's 
skin, it may be boiled without injury, so that a surgeon's 
glove made from it may be dipped into a formaldehyde solu- 
tion and then boiled for the purpose of cleansing, disinfection, 
and sterilization, which is a matter of great importance. 

This leather is applicable to a great variety of purposes. 
For example, it is exceedingly well adapted for ink ribbons; 
as a covering for balloons it has been found superior to the 
ordinary silk covering by virtue of its greater lightness, less 
bulk, pliability, softness, and imperviousness ; it is also used for 
partitions in dirigibles; it can be dyed any color, and when 
dyed, may be used in place of ornamental papers. This material 
serves the same purpose as the outer peritoneal coating of the 
caecum or blind gut of the ox, and is known as "gold-beater's 
skin," being used by the gold-beater in making gold leaf. In 
most of the slaughtering establishments in the United States 
and Germany this membrane is now removed from the intes- 
tine which it envelopes, and is supplied in this condition to the 
manufacturers of gold-beater's skin, or to gold-beaters. 

In order to convert this delicate membrane into leather, all 
fatty substances and adhering impurities are first removed by 
the following treatment : The membranes are rinsed in warm 
water, preferably in three graded baths, each having a higher 
temperature than the preceding one; for example, 77, 86, and 
95° F. One hundred membranes are next immersed, and left 
for about 5 minutes, in a bath composed of 10 grams of po- 
tassium permanganate dissolved in 3 liters of water and hav- 
ing a temperature of 80° F. They are then placed in a bath 
of 20 grams of sulphurous acid dissolved in 3 liters of water 
at 80° F. The skins must be left in this bath until they have 
swelled up and attain a pure white color, whereupon they are 
taken out and again submitted to three rinsings in warm water 
as above. They are now ready to be immersed in a soap solu- 
tion or bath. This is preferably prepared by boiling about 



210 PRACTICAL TANNING 

\ kilogram (1.1 lb.) of good pure white toilet soap, such as 
white castile, in 1^ liters (2\ pints) of water, for 100 mem- 
branes. The temperature of this bath has first to be reduced 
to 95° F. by the addition of | liter of cold water. The mem- 
branes remain in this soap bath for several hours, until the 
soap has been completely absorbed; they are then put suc- 
cessively into two baths of warm water having a temperature 
of 80° F., for the purpose of completely washing them. The 
membranes are now ready for the tanning process, which is 
as follows : A solution is prepared by dissolving, for each 100 
membranes, 100 grams of chromic acid, and 50 grams of alum 
in 1 liter of water at 95° F. The membranes are placed in 
a bath of 1 liter of warm water at 80° F., and the chromic 
acid solution is gradually added to the water, the skins being 
stirred in the bath. Preferably the following course is pur- 
sued : First, about a sixth of the chromic acid solution is add- 
ed to the membranes, then after about 10 minutes a further 
eighth of the same, and after another 10 minutes a quarter 
of the original amount of the chromic solution, and finally 
after 20 minutes, the rest of the solution is poured into the 
bath containing the membranes. In this final bath the skins 
are allowed to remain for an hour, being constantly agitated 
or stirred. They are then removed and rinsed twice with 
warm water at 80° F. This completes the tanning process. 

It is advantageous to immerse the tanned membranes in a 
bath composed of 500 grams of egg-yolk and 100 grams of 
glycerine added to 2 liters of water, and thoroughly mixed with 
it. The membranes remain in this bath for about 10 hours. 
They are then removed and drained by hanging over ropes, 
and are next placed on suitable frames and allowed to dry. 
After about 8 days they are stored in moderately damp cham- 
bers and are then drawn over their entire surface across cres- 
cent-shaped blunt knifes until they are smooth and pliable. 

The leather is now finished and may be used in this condi- 
tion, but for many purposes it may be found desirable to 
finish or embellish it further. It can be dyed beautiful colors, 
and for this purpose may be immersed in a bath containing the 



CHROME TANNAGE 211 

desired dye, such as aniline dye. A bath containing from 3 
to 5 per cent of dye usually suffices. To this bath is added a 
mordant consisting of 4 cubic centimeters of acetic acid of 
50 per cent strength. The leather remains in this bath for 
several hours. It is also claimed that by this process the 
leather, whether dyed or undyed, may be still further finished 
by passing it through calendering rolls. In some cases col- 
ored talcum powder may be sprinkled or dusted over it, and 
then calendered. It is also desirable in some cases to coat the 
undyed leather with a thin film of a composition prepared by 
mixing 8 parts collodion, 1 part castor oil and 1 part caout- 
chouc solution. Leather so coated is suitable for gloves, ac« 
cordion bellows, and the like. When it is desired to obtain a 
thicker and stronger leather, which, however, is not so well 
adapted for dyeing, a tanning bath consisting of 100 grams of 
zinc sulphate, 40 grams of alum and 50 grams of wheat-flour 
properly mixed with 1 liter of water, may be used to tan 100 
membranes, the other conditions and steps of the process re- 
maining the same. This tanning bath is used instead of the 
chromic acid bath described. This treatment yields white, 
lusterless leather of greater body than that produced by the 
chromic acid method. This process was patented by Bruno 
Trenckmann, of Berlin, Germany, who also has a patent on 
the following process : 

Parchment-like skin. — In the process as usually carried out, 
the peritoneal membrane of the gut, after having been cleaned 
of fat and soaked in a bath of soap, is immersed in a bath of 
zinc sulphate, barium chloride, or any other similar mineral 
salts which are able to produce pigments insoluble in water, 
by double transposition with any organic salts, acids, or bases. 
This process consists of alternately treating the skins in such 
baths at certain definite temperatures. For example, the gut 
membranes are first rinsed from 5 to 10 minutes in a solution 
of zinc sulphate or other mineral salts of 15° Be., and at a 
temperature of 40° F. They are then put into a solution pref- 
erably of sodium carbonate of about 15° Be. and at the same 
temperature, and are treated therein for about the same pe- 



212 PRACTICAL TANNING 

riod, raising the temperature to 60° F. They are then returned 
into another solution of zinc sulphate and then into a solution 
of sodium carbonate. This treatment is repeated once or 
twice more until the skins have absorbed a sufficient amount 
of the pigment, which is usually attained after two or three 
treatments. 

By this process a parchment-like, clear white, or well col- 
ored, product is obtained, which may come into contact with 
water and when again dry, will appear as before. The prod- 
uct is capable of being extended when soaked, and will again 
shrink while drying, thus making a tight cap, perfectly air- 
tight, so desirable for closing bottles of all kinds. 

Leather for organ pipes. — Leather made by the following 
process is distinguished by its fineness, suppleness, lightness, 
and durability. Such properties are required for many indus- 
trial purposes, particularly for fitting organ pipes, and in the 
manufacture of bellows and the like; and generally for pur- 
poses where it is desired to have an air-tight, light, and flex- 
ible material. The leather hitherto used for such purposes was 
usually not air-tight or sufficiently flexible, while rubber sheets 
or fabrics impregnated with a solution of rubber, although 
air-tight, are difficult to fit snugly because they are not suffi- 
ciently soft. They have also the serious drawback of being 
liable to deteriorate and lose their flexibility, thereby becoming 
brittle under the influence of cold. This is of great impor- 
tance in church organs which are not heated during the winter. 
This leather has none of these disadvantages, and is therefore 
suitable for various purposes. It is manufactured from the 
caecum or blind gut of the animal. This outermost skin of 
the blind gut has hitherto been deprived of its fat and dried, 
and used as the so-called gold-beater's skin. It has been pro- 
posed to subject it to a tanning process, but the leather ob- 
tained in that way alone is not sufficiently air-tight and durable. 

By means of this process, the blind gut skin, well cleaned 
and washed with potash or the like, is first tanned by mineral 
salts such as chrome-alum, etc., or with vegetable products. 
In practice, it has been found that for 200 skins of maximum 



CHROME TANNAGE 213 

size, 400 grams of zinc sulphate with 10 liters of water is suit- 
able as a tanning solution; or about the same quantity of 
chrome-alum may be used. The skin is then filled in a bath 
of egg-yolk, flour, or the like, and permitted to remain therein 
until it is thoroughly impregnated, whereby it is made thicker 
and stronger. This bath is made by adding a small quantity 
of flour to about 1 liter of egg-yolk. The skins are then rinsed, 
stretched, and dried. The drying is effected by placing two 
skins, one on top of the other, and allowing to dry together 
in close contact. During this drying process they adhere firmly 
to one another without any glue or cement being used. The 
best plan is to place together the grain or outermost sides of 
the two skins. More than two skins may be superposed, in 
which case the similar sides are placed in apposition. 

When a multiple skin treated in this manner has become 
sufficiently dry it is de-greased or deprived of its fat by treat- 
ing it with benzine, being rubbed and kneaded at the same time, 
whereby it is rendered soft and supple. This treatment is 
necessary to remove the oil incorporated in the skin by treat- 
ment with the eggs, and make the leather soft and capable of 
being cemented to wood and metal. This property renders it 
suitable for gluing or piecing together, so that large pieces 
of any size may be made from small pieces, and it can be ce- 
mented to other materials, such as wood, etc., which is of im- 
portance for organ pipes and other purposes. This process, 
as stated, includes the process of tanning the stock, but if un- 
tanned skins are subjected to the other steps of the treatment 
— filling, superposing, and washing with benzine — a product is 
obtained having many • advantageous characteristics over the 
untanned skins previously known. 



CHAPTER VII 
IRON TANNAGE 

The subject of iron tannage has been much discussed, and 
many attempts have been made to obtain a satisfactory tan- 
nage with this element. Iron belongs to the same periodic 
group as aluminum and chromium, and naturally one would 
expect it to lend itself to the same general reaction as the other 
two elements. Of the three elements, iron is the most basic, 
and, unlike chromium and aluminum, has no acid-forming 
property. The tanning quality of iron, however, does not de- 
pend upon this property, but rather upon the fact that it forms 
basic compounds when its salts are treated with an alkali. Al- 
though chromium and aluminum also form basic products, 
these compounds are more stable than that produced from 
iron. Any attempt to produce a compound of the formula 
Fe2(OH)2S04 will result in the precipitation of the hydrated 
oxide Fe2C>3. H2O which is a yellow powder and entirely in- 
ert as a tanning material. This hydrated oxide differs also 
from the corresponding aluminum and chromium oxides in 
that it rapidly passes through the colloidal range and becomes 
a crystalline substance. 

In a series of papers which appeared in the Journal of the 
American Leather Chemists' Association, beginning in the 
February issue of 1921, Dr. Daniel D. Jackson and Dr. Te 
Pang Hou set forth the early history of this important sub- 
ject, and through their investigations have shown conclusively 
why so many attempts to produce iron-tanned leather have 
failed. They have also pointed the way to new processes 
which open up a new field for investigation and should warrant 
every consideration. 

Having had Dr. Hou as a student at one time, and know- 
ing the painstaking care with which the investigation was con- 
ducted; the author can vouch for the thoroughness of the clas- 

214 



IRON TANNAGE 215 

sic research, and desires to give him credit for the following 
information on iron tannage : 

Research in iron tannage. — Attempts to use iron salts as 
tanning agents date back to the time when efforts were first 
made to find a substitute in the form of metallic salts for vege- 
table tannins. In the course of more than a century, efforts 
were repeatedly made and interest was continually revived to 
make iron tannage a commercial success, but without reward, 
in spite of the great promise that inspired such investigators to 
make a most determined effort. Within the last decade, partly 
on account of the great war, new interest has been given to 
iron tannage, and the properties and behavior of iron salts 
as tanning agents are gradually becoming better understood. 

The history of iron tannage begins from the latter part of 
the 18th century. Many of these early investigators were 
men who also helped to establish the present-day chrome 
tannage. 

In 1770, J. Johnson, an Englishman, patented a process 
of tanning, using ferrous sulphate with an acid (sulphuric 
acid, hydrochloric acid, or nitric acid). The pelt was tanned 
in three operations, in the middle of which a vegetable tannin 
was used. 

In 1794, Sam. Ashton, another Englishman, recommended 
for tanning a mixture of iron oxide and sulphuric acid, cal- 
cined iron ore or iron ocher with pyrite, copper ore, and zinc. 
The period of tanning was given as from 5 to 7 weeks. Some 
alumina was added for calfskins. 

In 1805, Sigmond Hermbstadt, in his book on leather tan- 
ning, explained that solutions of metallic acid baths had simi- 
lar action on the pelt as oak tannins. Among other salts he 
mentioned the red iron sulphate, in which not only the grain 
of the pelt was affected, but the pelt was virtually converted 
into leather if soaked in it for some time. He prepared his 
iron tan liquor by heating ferrous sulphate to a dry yellow 
substance which was dissolved in 20 times its volume of boil- 
ing water, and on cooling, the clear yellow-red solution was 
decanted for use. He also treated iron oxide with acetic acid ; 



216 PRACTICAL TANNING 

or oxidized ferrous sulphate with concentrated nitric acid, or 
with a mixture of concentrated nitric acid and sulphuric acid. 
Sole leather as well as upper leather could be made in this way, 
but it was de-tanned in contact with water. 

In 1842, d'Arcet, a Frenchman, tanned the hides in a ferric 
sulphate solution, but the sulphuric acid set free gradually de- 
stroyed the hides. In the same year, Julius Bordier, of London, 
patented a process (British patent 9,219, 1842) of oxidizing 
ferrous sulphate with nitric acid and sulphuric acid, and with 
manganese dioxide and sulphuric acid. It was said that he 
had attained some success. 

In 1853, Hylten Cavalin, employed a tanning liquor con- 
taining 10 lb. of potassium dichromate and 20 lb. of alum in 
180 lb. of water. The hides were tanned in this liquor for 4 
days, and were next placed in a 10 per cent ferrous sulphate 
solution for 12 hours with frequent stirring. The acidity re- 
lation of these two liquors was not properly adjusted, and the 
iron was not completely oxidized. The leather obtained was 
hard and brittle. 

In 1855, Rene de Kercado Molac and Jean Daniel Friedel, 
both of Strasbourg, France, patented a process whereby the 
hides were tanned in a basic ferric sulphate solution which 
was later neutralized with metallic oxides, such as ferric 
oxide, alumina, and zinc oxide to remove the sulphuric acid 
liberated. They prepared the liquor with ferrous sulphate, 
manganese dioxide, and sulphuric acid, and added ferric ace- 
tate in varying proportions to the liquor. A. E. L. Bellford, 
of London, patented their process in England. In this Brit- 
ish patent (January 12, 1855) it was stated that the leather 
treated by other mineral processes is "liable to tear in length 
of time on account of the great quantity of acid remaining in 
the leather corroding the animal fibers." 

Dr. Frederick Knapp, Professor at the Polytechnic School 
of Braunschweig, Germany, made a thorough investigation on 
these mineral tannages and published the results in "Die Natur 
und das Wesen der Gerberei und des Leders" (Munich, 1858), 
and also in an article, "Uber Gerberei und Leder," in Dingler's 



IRON TANNAGE 217 

Polytechnische Journal, vol. 181, p. 311 (1866). He made a 
satisfactory explanation of the tanning action. He had in mind 
the possibility of reducing the length of time needed in the 
vegetable tanning process, and eliminating costly materials 
such as egg-yolk and flour used in alum tannage. He recog- 
nized the plumping effect upon the hides by the acid liberated 
during tanning, and the stiff and brittle character of the leather 
obtained. He recommended neutralizing the tan liquor dur- 
ing the process of tanning with sodium carbonate or caustic 
soda, and pointed out the advantages in so doing, namely, that 
the hides were more richly tanned, that the harmful acid ef- 
fect was prevented, and that neutral electrolyte NaCl (in 
FeCl 3 liquor) was produced in the tan liquor. His British 
patent 2,716 (1861), through John H. Johnson, covered iron, 
chrome, manganese, and other metallic salts in combination 
with fatty acids to form insoluble metallic soaps, so that the 
iron in the pelt might not be washed out. He also mentioned 
the use of similarly insoluble silicates of alumina and alkaline 
earths. According to his German patent No. 444 (1887), he 
prepared his liquor by adding nitric acid in excess to oxidize 
completely a boiling ferrous sulphate solution when brown 
nitrogen dioxide (N0 2 ) fumes were seen. After all of the 
iron was oxidized, he introduced more ferrous sulphate into 
the resulting solution, as long as N0 2 fumes were evolved. 
The liquor, after evaporation, becomes a varnish-like liquid. 
Judging from this description; his liquid must have been too 
alkaline through the loss of the nitric acid by boiling. In his 
additional German patent No. 10,518 (1879), he used sodium 
nitrate and sulphuric acid for oxidation instead of the nitric 
acid. This method is far more economical, and involves no 
danger of losing the acid by heating, so that the acidity of the 
resulting liquor is under control. Furthermore, a neutral salt, 
Na 2 S0 4 , is produced in the tan liquor. 

In 1864, F. Pfannhauser obtained a patent for the prepara- 
tion of a basic ferric sulphate solution and its use in tanning. 
He roasted ferric sulphate to a red heat with continuous stir- 
ring until it was reduced to a red powder, which was then 



218 PRACTICAL TANNING 

thrown into water while still hot. Most of this powder was 
said to be dissolved. The colloidal matter was allowed to 
settle, and the supernatant liquid was drawn off for prepara- 
tion of tan liquors of varying strength. The skins were tanned 
counter-currently and, when tanned, were placed in a soap 
solution. 

In 1877, Paesi proposed to use a ferric chloride solution 
together with salt at 20° C. in the ratio of 100 parts of water 
to 10 parts of FeCb and 5 parts of salt. 

In 1881, E. Harcke obtained a German patent, No. 19,633, 
according to which the pelt for making sole leather was treat- 
ed with a mixture of a resinous body (such as rosin), coal-tar 
creosote or carbolic acid, and an alkali, in water, until thor- 
oughly penetrated. The pelt was then tanned, first in an 
aluminum salt solution and then in a ferric chloride solution, 
or other ferric salt solution. For making upper leather, the 
hides were previously limed, and if softness and porosity were 
desired, the rosin could be omitted. 

In 1881, W. Eitner patented a process (Austrian patent No. 
6,775) using a mixture of a basic chromic sulphate and ferric 
sulphate solution. This process was used in Graz, Austria, 
and the product known as "patentleder, marke elefant." By 
changing the ratio of the chromic salt to the ferric salt, dif- 
ferent gradations of color — from yellow (of the iron) to 
gray (of the mixture) and to green (of the pure chrome) — 
were obtained. When a mixture of the ferric and chromic 
salts was used, the leather was colored black with logwood 
alone; when chromic salt alone was used, the leather was 
colored black with logwood and an iron "striker." When a 
yellow color was not desired in the product, chromic salt alone 
was used for tanning. Leather obtained in this way was stuff- 
ed, after sammying, with mixtures of train oil, castor oil, 
stearine, tallow, mineral oil, etc., with sodium bicarbonate, 
soap, borax, casein, etc., as emulsifying agents. 

In 1886, John W. Fries, of Salem, North Carolina, pat- 
ented a process of tanning (U. S. patents No. 343,166 and 
343,167), using ferrous carbonate (or ferrous sulphate), so- 



IRON TANNAGE 219 

dium carbonate (or sodium bicarbonate), and sulphuric acid. 
The skins were tanned first in a dilute liquor for 2 or 3 days, 
and then in a more concentrated liquor for the same length of 
time. A small amount of liquor might be added. After the 
tanning operation the skins were hung in the air to get the 
iron oxidized. For currying, he used tallow with a paraffin 
oil, lard, or cotton-seed oil ; and later, in his patent No. 343,- 
167, he recommended an alcoholic solution of castor oil. 

In 1892, Paul F. Reinsch of Erlangen, Bavaria, patented a 
process (German patent No. 70,226) using a liquor prepared 
by mixing 10 kg. (kilogram) FeCl 3 dissolved in 40 liters of 
water, with 4^ kg. crystalline Na 2 C0 3 dissolved in 20 liters 
of water, thus yielding a dark brown solution. He called it 
ferric chloride-sodium chloride liquor, which he used for mak- 
ing different kinds of leather, either alone or in combination 
with alum-sodium chloride tannage. In 1912 he obtained an- 
other German patent, No. 265,914, on the use of ferric chlo- 
ride and magnesium carbonate. He prepared the liquor by 
dissolving 1 kg. of ferric chloride in 4 liters of water, to which 
was added a suspension of 225 grams of MgCO s in a liter of 
water. To this mixture he added a solution of 8 per cent 
aluminum chloride. Evidently his idea is to bring about the 
required basicity by MgCOs- The A1C1 6 present was probably 
meant to help keep the basic ferric chloride in solution. 

J. Bystron, and Karl, Baron von Vietinghoff, obtained a 
number of German patents, No. 255,320 et seq., in 1911, a 
British patent, No. 13,952, in 1912, and two U. S. patents, 
No. 1,048,294 in 1912 and No. 1,061,597 in 1913. They em- 
ployed nitrogen dioxide (NO2) and nitrogen trioxide (N 2 3 ) 
for the oxidation of iron. The nitric oxide (NO), from the 
oxidation reaction is collected and re-oxidized by contact with 
fresh air to N0 2 and N 2 3 , which gases are used again for 
oxidation. They thus proposed to utilize the N0 2 -NO-N0 2 
cycle, making the oxides of nitrogen virtually catalytic agents 
for the oxidation of iron. In British patent, No. 13,952 they 
observed considerable precipitates formed in the tan liquor 
and on the skin. According to them the presence of large 



220 PRACTICAL TANNING 

quantities of an acid causes the formation of a highly acid 
and not completely insoluble iron oxide in the skin, so that 
the leather made is brittle and cannot be stored. In this patent 
and also in the U. S. patent No. 1,048,294 they proposed 
placing the skin in a ferrous salt solution, and oxidizing the 
ferrous iron by passing in NO2 gas from outside or by liber- 
ating HNO2 from a nitrate added to the liquor. Thus they 
attempt to complete the oxidation reaction and the tanning 
operation in a single operation. It is true that HNO2 (from a 
nitrate and an acid) has sufficiently high oxidation potential 
to oxidize ferrous iron to the ferric state, but in order to oxi- 
dize all the ferrous iron into the ferric state completely, the 
presence of much acid in the solution and of an excess of 
the oxidizing agent is needed. If the oxidation by HNO2 or 
oxides of nitrogen is to take place simultaneously with the 
tanning operation at the low acidity necessarily present in the 
tan liquor, probably there will be much difficulty in getting 
all of the ferrous iron completely oxidized. Bystron, in U. S. 
patent No. 1,061,597, patented the use of a neutral alkali salt 
such as Na2S04 or NaCl for treating the iron-tanned leather. 
He claimed that by this treatment a more insoluble basic fer- 
ric salt of a light color is formed in the leather, thereby yield- 
ing a soft, elastic, and non-brittle product. 

In 1917, O. Rohm obtained British patents No. 103,827 and 
104,338 for a combination tannage using formaldehyde and 
ferric chloride, or formaldehyde and a mixture of ferric chlo- 
ride and chromic chloride or aluminum chloride. In his patent 
No. 103,295 (not accepted) he mentioned the use of ferric 
alum mixed with vegetable tannins to form iron tannate (ink) 
for tanning. In his patent No. 103,827 he recommended tan- 
ning with formaldehyde in sodium bicarbonate solution, fol- 
lowed by a tannage with a ferric chloride solution; a mixture 
of ferric chloride and chromic chloride ; a mixture of ferric 
chloride and aluminum chloride ; a ferric chloride solution and 
then vegetable tannins; or a ferric chloride solution with an 
alkaline sulphide. He also mentioned the treatment of the 
skin with an iron precipitant, such as NH3, alkalies, or alkal- 



IRON TANNAGE 221 

ine salts ; or phenols, naphthols, organic carboxylic acids, vege- 
table tannins; or soap, sulphide, polysulphide, and the like. 
He mentioned that the leather obtained would not become slip- 
pery when wet, as is the case with a chrome leather. In his 
patent No. 104,338 he stated that the aldehyde tannage could 
be advantageously used to follow iron tannage after neutral- 
ization, or together with neutralization. When the aldehyde is 
introduced with the neutralization after the iron tannage, there 
is, according to Rohm's observation, an advantage that the 
grain-drawing, so common in mineral tannage, will be pre- 
vented. His thought seems to be along the line that since aide" 
hyde tannage is carried on in an alkaline solution, the intro- 
duction of the aldehyde tannage after the iron will serve also 
as a neutralization operation to fix the iron in the pelt. But 
since formaldehyde is a tanning agent alone, to what extent 
the iron salt has contributed to the tannage it is difficult to tell. 
In his German patent No. 306,015 (1918), Emil Kanet in- 
troduced an interesting feature in the mode of tannage. He 
derived the tanning action by the hydrolysis of a ferric salt. 
He treated the pelt at a low temperature with a ferric salt 
solution of such a basicity that it would be unstable at the 
ordinary temperature; and, after allowing the liquor to pene- 
trate the pelt, raised the temperature to bring about hydrol- 
ysis. To illustrate : He placed the skins in a basic ferric ace- 
tate liquor containing from ^ to 2 J per cent of Fe203, prefer- 
ably with the addition of some salt or other electrolyte such as 
sodium acetate. After the skins were penetrated by the tan- 
ning liquor he transferred them to a fairly concentrated salt 
solution at a temperature of from 45 to 60° C, or exposed 
them to heat in a warm chamber. The tanning action was 
completed in a short time, but the stock was further laid aside 
for some time to fix the iron. The acetic acid set free under 
the influence of heat can be recovered from the skins by pres- 
sure. If a filling material such as flour is used with the tan 
liquor, it is, according to him, fixed in the leather with the 
basic ferric acetate. Other mineral salts such as chromic salt 
can be mixed with the iron. The advantage claimed is that 



222 PRACTICAL TANNING 

at a low temperature a more basic ferric salt solution can be 
used, and that the oxidizing activity of the ferric iron towards 
the skins is lessened. 

In his Swiss patent No. 75,775 (1918), W. Mensing recog- 
nized the ease with which ferric salt in solution is decomposed, 
and mentioned the effect of ferrous iron on the skin when the 
ferrous salt is present in the tan liquor. He recommended 
the use of an excess of an oxidizing agent and patented the 
use of a chlorate (Na, K, or Ba) as the oxidizing agent. He 
also recommended a preliminary treatment of the skin with 
borax or a basic aluminum or chromic salt solution for the 
use of a slightly more acid or neutral ferric liquor. Accord- 
ing to his idea, the tanned stock should not be washed with 
water, but only wrung or pressed to get rid of the excess of 
the tan liquor. On drying, the stock is oiled with a mineral 
oil, paraffin, or ceresin, and then washed. To avoid reaction 
of the iron in the pelt with vegetable tannins, he recommended 
fixing the iron by treating the leather with a slightly alkaline 
solution before vegetable re-tanning. He advocated the 
bleaching of the leather by de-tanning the surface layers by 
means of a reducing agent and then an acid. On the whole, 
his patent marks a better understanding of the properties of 
the iron tan liquor and the process of iron tannage. 

Vittorio Cassaburi, in the articles, "Notes on the Tannage 
of Skins with Iron Salts," published in the Journal of the 
American Leather Chemists' Association in 1919, gave the 
results of a series of his experiments, using a basic ferric 
sulphate solution (from the oxidation of ferrous sulphate with 
a mixture of nitric acid and sulphuric acid) ; a solution of a 
mixture of basic ferric chloride and sulphate (from the oxida- 
tion of ferrous sulphate by nitric acid and hydrochloric acid) ; 
a basic ferric chloride solution, and a basic ferric acetate solu- 
tion. He employed a strength of iron liquor containing 1 per 
cent of Fe20s on the weight of the pelt in a little over 4 times 
the weight of the water as of the weight of the pelt. Accord- 
ing to him, 7.88 per cent of Fe20s in the leather on the basis 
of the dry weight is sufficient to convert the pelt into leather. 



IRON TANNAGE 223 

He stated that he had started with a tan liquor having such 
a basicity as to correspond to the formula Fe2(S04)s(OH)2 
but his iron and basicity determinations of the liquor showed 
that the liquor he used was more acid than this, the basicity 
of his first liquor (basic ferric sulphate) being only one-half 
of this value, and that of his second liquor (a mixture of 
basic ferric sulphate and chloride) less than a half of this 
value. (We have found that a sulphate liquor having so high 
a basicity as to correspond to Fe2(S04)2(OH)2 is too alka- 
line for use.) Throughout the course of tanning he strength- 
ened the liquor with fresh portions of the strong liquor. 

In his work, Dr. Hou devoted much time to the study of 
proper methods for the oxidation of the ferrous to the ferric 
conditions, and made a careful series of tests on the exact 
point of neutralization. All of this work is set forth in his 
treatise referred to early in this chapter, so it is hardly nec- 
essary to repeat it in this volume. Dr. Hou's conclusions may 
best be stated in his own words, showing that iron tan- 
nage has possibilities when the processes are conducted along 
scientific lines : 



The character of the iron tannage seems to lie between that of alum 
and chrome tannage. Iron seems to yield a more permanent tannage 
(towards water) than alum, but like the alum tannage, iron-tanned leather 
does not resist the boiling temperature of water. If we take the critical 
temperature as that at which the sample under water begins to shrink or 
to draw together under the influence of heat, that point generally lies 
between 160° and 175° F. In the case of a re-tanned leather (in fish 
oils or vegetable tannins) a somewhat higher test may be obtained; but 
in no case can an iron-tanned leather stand boiling, unless a considerable 
portion of the tannage is due to chrome as in the case of the chrome- 
iron joint tannage. 

It has often been reported that iron-tanned leather produces a brittle 
grain, and rots on storing, but to do justice to the iron tannage it must 
be declared that an iron-tanned leather, properly tanned, is not brittle on 
the grain and does not deteriorate on storage. Samples of leather which 
have now been kept for more than 10 months show no sign of deteriora- 
tion. Sometimes the product obtained is somewhat stiff and "flat," but this 
should not be ascribed to the inherent properties of the tannage. The 
strength, the fullness, the elasticity, are, in our opinion, a matter of 
proper tannage and not dependent upon the nature of the tannage. 

As a considerable amount of salt (4 to 5 per cent of the weight of the 
pelt) is needed in the liquor, and much of it is formed from neutralization, 
it is important to rinse the tanned stock after neutralization to wash off 
most of the neutral salts present (NaCl, Na 2 SC>4, etc.) ; otherwise their 
presence in the leather may cause dampness or even salt stains or spues. 
Iron tannage is much affected by the presence of grease or any imperfec- 



224. PRACTICAL TANNING 

tions in the skins, and when such is the case, unevenness of color and other 
irregularities are liable to show up on drying; hence the necessity of 
uniform softening of the pelt and of de-greasing. 

Iron-tanned leather generally runs high in ash. The leather often has 
a harsh feel, due probably to the presence of a large amount of iron 
oxide (Fe 2 3 ) in the leather. On account of this harsh feel it is generally 
advisable to give the leather a somewhat heavy fat-liquoring or an oil 
treatment. The use of flour, egg-yolk, etc., may be practiced, if desired. 
At the present stage of our knowledge it seems that to produce a satis- 
factory tannage, at least for a light leather, an amount of iron, calculated 
as Fe 2 3 , not less than 4 per cent of the weight of the air-dried sample 
should be present. 

The iron-tanned leather compares favorably with other mineral-tanned 
leather. The red-yellow or brown-red color of the tannage, however, is 
for some purposes an undesirable feature. The chemical activity of iron, 
forming dark colored compounds in the leather, is another drawback. But 
even with all these limitations there is much to be said in its favor. There 
are certain classes of goods in which these features are of no consequence 
and the saving in the cost of production is considerable. True, there 
are difficulties in connection with the tanning operation and subsequent 
treatment of the leather — difficulties which in other tannages either do 
not exist, or are less serious. But the process, like any other new process, 
necessitates a new set of conditions. To summarize, the following main 
factors may be mentioned : 

I. Completeness in the oxidation of iron and maintenance in its ferric 
state by using an excess of a proper oxidizing agent, and by means of an 
after-oxidation. 

II. Adjustment of proper basicity by the addition of a proper amount 
of an alkali, a basicity between the ratio of one OH-equivalent to every 
5 equivalents of the mineral acid radical present, and that of one OH- 
equivalent to every 3 equivalents of the mineral acid radical present, being 
the proper range for tanning. 

III. _ Gradual neutralization to be effected so that iron may be uniformly 
fixed in the pelt throughout its thickness. 

IV. Drying to the crust state before subsequent treatment to minimize 
the chemical reactions between the iron in the stock and the substance 
employed, which would react with iron to give an undesirable color. 

It might be added that the subject of iron tannage presents 
a broad and unexplored field, and this study is far from being 
exhaustive. Other phases could have been taken up and it is 
hoped that this work will serve as an indication for much 
that remains to be done. 



CHAPTER VIII. 

VEGETABLE-TANNED LIGHT LEATHERS 

The processes employed in the production of leather with 
vegetable tanning materials vary according to the kind of 
leather being manufactured, and with the nature of the ma- 
terials employed. Time is also an important factor, and 
several months may be consumed in the case of sole leather, 
while with light leather the operation may be completed in a 
few hours. In dealing with these processes the study of 
light leathers will be considered first. 

Vegetable-tanned sheepskins: Quebracho tannage. — ■ 
Soft and well-tanned leather is made by tanning pickled sheep- 
skins with quebracho extract. This tanning material is used 
alone with good results; it is also used in combination with 
chestnut and hemlock extracts. It is recommended that for 
the quebracho tannage the skins be pickled with formic acid 
and salt. When so pickled and carefully tanned, they have 
fine, soft grain, and there is no danger or difficulty in dyeing 
owing to lime spots. The natural grease should be removed by 
pressing the skins while they are in the pickled condition. It 
is also advisable to press them after they have been colored 
in the first quebracho liquor ; they are then put back into the 
liquor and tanned thoroughly. The quebracho liquors should 
always contain salt. A quantity of the extract is boiled with 
water in a barrel, this forming a stock solution from which 
the tan liquors are made and strengthened. 

To make the first liquor, add enough of the dissolved 
extract to water in a paddle to make a 3 or 4° bk. liquor. 
Let the skins turn in this liquor until they have assumed 
a uniform color and are well struck with the tan; then 
either strengthen the liquor, or pass the skins into a fresh 
and stronger liquor of 6 or 8° strength. After several hours 
the liquor is strengthened to 10°, and the skins are left therein 

225 



226 PRACTICAL TANNING 

until they are completely tanned. The skins can be taken 
out of the paddle after the grain is set, and tanned out in a 
drum, thus saving time. 

When it is fully tanned, the leather is washed and fat- 
liquored with a solution of sulphonated oil or some other fat- 
liquor, and dried; or it is dried and fat-liquored after dyeing. 
The skins can be tanned by being tacked to wooden strips 
or frames, and suspended in the liquor. The tanner must be 
careful to avoid drawn grain by having the liquors too strong 
at the beginning. The liquor for the fresh skins should not 
be over 6 to 8° strength; but as soon as the grain is well 
set, the liquor can be strengthened. Colored and embossed, 
the skins make fine leather for pocketbooks and bags, sweat- 
bands for hats, and other purposes. 

Hemlock and quebracho tannage. — In this process the skins 
are started in weak hemlock liquor, and then passed into a 
stronger liquor composed of hemlock, oak-wood and que- 
bracho extracts, care being taken to handle the skins every 
day until they are tanned. Hemlock and quebracho extracts 
combined form a good tan for sheepskins. The liquor may 
be two-thirds quebracho and one-third hemlock. The result- 
ing leather is tough, firm, and pliable; and has good color 
which is more satisfactory in every way than the color of 
hemlock leather. 

Hemlock tannage. — Large quantities of sheepskins are 
tanned with hemlock-bark extract, and used for various pur- 
poses. The tannage fills and plumps the skins, and the leather 
has good color on which it is easy to apply dyes. Hemlock- 
tanned skins are finished in the natural color of the tan; they 
are dyed black or colored, and are finished with a smooth 
or an embossed grain for fancy leather purposes. 

Pickled skins should be pressed for removal of the grease, 
and drummed in warm salt water to soften and open them 
out, also to separate and prepare them for the tannage. There 
should be considerable salt in the liquors. The tanning is 
begun in weak liquor, which is gradually strengthened until 
the skins are tanned through. When tanned, the leather is 



VEGETABLE-TANNED LIGHT LEATHERS 227 

horsed-up to drain, dried, then colored and finished. A mix- 
ture of oak and hemlock liquors produces light-colored, well- 
tanned leather. 

Combination tannage. — A mixture of gambier, alum, and 
salt can be recommended for making a soft, durable leather 
from sheepskins. The skins are limed and drenched in the 
usual manner, and are then placed in gambier liquor in a 
paddle. From 3 to 5 lb. of gambier is sufficient for a dozen 
skins, according to size and thickness. After the skins have 
started to absorb the gambier, from 8 to 16 oz. of alum and 
8 oz. of salt for each dozen skins are added to the liquor, and 
the paddling is continued until the tannage is completed. The 
leather is then washed in warm water to remove the adhering 
tan, and then treated with acid fat-liquor, dried, wet-back, 
colored or blackened, dried again, and finished. 

After the alum and salt are added, it is customary to put 
the skins and tanning liquor into a drum, and run a few 
hours or until the skins are thoroughly tanned. Some soluble 
oil may also be added to the liquor and applied to the leather 
toward the end of the tanning process. Excellent leather is 
also made by taking the skins out of the gambier liquor when 
they are well struck through, striking them out, and then 
drumming them in a paste of water, flour, alum, salt, and 
either egg-yolk or sulphonated oil, drying, and then coloring. 
Quebracho extract may be used in place of gambier, with 
equally good results. The color of the tanned leather can 
be greatly modified by adding a solution of fustic or other 
dyewood to the gambier liquor. The entire process can also 
be reversed. The skins can first be drummed in alum and 
salt, dried out, and staked, and then re-tanned with gambier. 
For glove leather, flour and oil may be added to the alum 
and salt liquor, the skins drying out soft and full. 

Heavy skins can be tanned with gambier, split, and shaved, 
and then re-tanned with gambier, alum, and salt ; they can 
also be alum-tawed, sammied, and shaved, and then re-tanned 
in a drum with gambier or quebracho. There are numerous 
variations of the process, these few suggestions being suffi- 



228 PRACTICAL JANNING 

cient to give some information about methods which may be 
used. After the leather is dry, it can be colored, and, if not 
previously fat-liquored, drummed' in acid fat-liquor or an 
emulsion of oil and soap, dried, staked, and finished. The 
product is a soft and durable leather, which is suitable for 
gloves, linings, and various other purposes. 

Sumac tannage. — Sumac makes soft, light-colored leather 
which can easily be colored and finished in any desired man- 
ner. The tannage is done in paddles ; the skins are then dried 
and finished. The first liquor is rather weak and mellow ; 
and as the tannage proceeds, the liquors are stronger and are 
warmed. A mixture of oak bark and sumac is also some- 
times used ; and a shorter tannage is obtained by drumming 
the skins with the tanning liquor after the grain has been set 
in a paddle. 

The use of sumac after the regular tanning process is 
complete is for the purpose of preparing the leather for 
coloring. When the skins are completely tanned, they are 
horsed-up over night and are then placed in sumac liquor. 
This is prepared by adding water at 122° F. to 25 lb. of 
best Palermo sumac. The liquor should be cooled to 90° F. 
before the skins are put in, then they should be stirred more 
or less and left in over night, drained, set out, and dried. 
Sumacking can also be done in a drum. If soft leather is 
wanted, the skins can be run in a solution of sulphonated oil 
before they are dried. When dry, they should be kept in 
storage-rooms for some time before being colored and finished. 

Well-tanned leather is made by a tannage of gambier and 
sumac. The skins are put into a 10° bk. liquor slightly acid- 
ified with acetic acid. After they have been in this liquor for 
a few hours they are placed in another and stronger liquor, 
and from this they are passed into a third and still stronger 
liquor to which acetic acid and oak-wood extract have been 
added. From this third liquor the skins are passed into the 
sumac bath, and are then oiled and dried out. 

The application of an alum or kid tannage to skins tanned 
with gambier or quebracho makes fine, soft dongola leather. 



VEGETABLE-TANNED LIGHT LEATHERS 229 

For 200 average skins, a mixture is prepared from 5 lb. of 
alum, 9 lb. of salt, 24 lb. of flour, 10 lb. of egg-yolk or a 
corresponding quantity of sulphonated oil and 8 gallons of 
water. The alum and salt are dissolved in part of the water, 
then the flour is stirred in. The egg-yolk or the oil mixed 
with warm water is next added, and the whole mixture is 
thoroughly stirred. The skins are drummed with the mix- 
ture for an hour, then dried, colored, and finished. 

Tanning with alum, sumac, and oak bark. — A soft, light- 
colored skin which can be used in the natural color of the tan- 
nage, or colored any desired shade, is made by tanning with 
alum, Glauber's salt, common salt, sumac, oak bark, nutgalls, 
and acid. 

The pickle should be removed from the skins by drenching 
them with whiting and salt, followed by washings in two 
baths of warm salt water. To make the tanning liquor, dis- 
solve 6 lb. of alum, 3 lb. of Glauber's salt, and 4 lb. of com- 
mon salt in 5 gallons of water; and in another tub, boil 5 lb. 
of ground sumac, 3 lb. of oak bark, and 1 lb. of ground nut- 
galls, in 5 gallons of water. Mix the two solutions, then 
strain while the mixture is hot. A small quantity of formic 
acid is added to preserve the color. 

The liquor is used lukewarm and the skins are drummed 
with it until they are tanned, then allowed to drain 24 hours. 
They are next struck out on both sides and oiled with neat's 
foot oil, then dried. A solution of sulphonated oil may be 
used instead of neat's foot oil; the skins can be drummed in 
it, or it may be applied by hand. The skins tan quickly, and 
when worked out can be colored any shade or left in the nat- 
ural color of the tan. The leather is durable and quite mois- 
ture-proof. 

Tanning with chestnut extract. — Sheepskins, prepared as 
for any other tannage, may be tanned by being hung in chest- 
nut liquor, or drummed in liquor made direct from the extract, 
or from a mixture of chestnut and quebracho extracts. If 
the skins are intended to be colored after they are tanned, 
it is best to tan them direct in the extract liquor, and then 



230 PRACTICAL TANNING 

re-tan them with sumac. Stock to be run in the natural 
color is usually struck in the combination liquor, giving the 
shade desired. With very thin skins, the main requirement 
of the tanning material is that it be clean, bright, and quick 
in action. Tanning may be started in a paddle and finished 
in a drum, the leather being then dried, treated with sumac, 
colored, fat-liquored with acid fat-liquor, dried, and finished. 

Tanning with sumac, alum, and salt. — Sheepskins may be 
tanned in sumac liquor and then placed in a solution of alum 
and salt for one day. Taken out of the latter solution, the 
leather is rinsed off, struck out, and oiled with sulphonated 
oil, hung up, and dried. Coloring can then be done with 
artificial dyestuffs — basic or acid — the skins are again dried, 
worked out soft, and finished. 

Quebracho-tanned sheepskins. — The pickled skins, being 
weighed, are placed in the mill and a solution of 30 per cent 
of quebracho extract on the weight of the stock is prepared 
at a concentration of 30° bk. To this solution is added 10 
per cent of salt on the weight of the stock, and the whole 
added to the stock in the mill. The mill is now run for 1-| 
to 2 hours, or until the stock is tanned. The plugs being 
drawn, water is turned on, and the stock is washed until per- 
fectly clean. If desired, washing may take place in a separate 
mill, and a new lot of skins run in the spent liquor for 
half an hour to utilize the unabsorbed tan. The plugs being 
drawn, a new liquor of 25 per cent of quebracho at 30° bk. 
with 10 per cent salt will be a sufficient quantity to complete 
the tannage. The plugs are then returned, the above liquor is 
added, and milling continued for 1-J hours. The washed stock 
is now fat-liquored with 1 per cent of anhydrous turkey red oil 
at a temperature of 110° F. for 30 minutes, washed again, set 
out, shaved, and hung up to dry. When dry, it is de-greased, 
buffed if necessary, and colored. 

Skivers. — A skiver is the tanned grain side of a split 
sheepskin. The skins are split either after they have been 
limed or pickled. The grains are then tanned the same as 
whole skins with sumac, bark, alum, or some other tannage. 



VEGETABLE-TANNED LIGHT LEATHERS 231 

Skivers are used in the manufacture of leather goods, for 
linings, hat sweat-bands, etc. They can be tanned with any 
material which is used in the tanning of sheepskins. Sumac 
is in common use ; quebracho extract and quermos and hem- 
lock extracts also make good skiver stock. If soft white 
skins are wanted, alum is used. Little tanning is required. 
It is generally sufficient to get the stock well struck through 
with the tanning material. 

A good tannage is a mixture of two-thirds quebracho and 
one-third hemlock extracts. This produces a light and uni- 
form color. 

Coloring and finishing are the same as for skins; but 
skivers, being very thin, require careful handling to prevent 
them from getting torn. 

Roller leather. — This leather is made from lambskins 
tanned with bark. The qualities needed are level substance, 
clear and perfect grain which has no scratches, scars nor cuts, 
smooth feel and pliability, with a certain degree of firmness. 
Only the best skins should be selected. The leather must be 
perfectly smooth on the grain, or the cotton thread used by cot- 
ton spinners — who use this class of leather — when it is drawn 
between the rolls, one of which is covered with leather, will 
keep breaking. As a light color is essential, only clean, light- 
colored bark liquors can be used. The natural grease con- 
tained in the skins must be removed since the edges of the 
leather covering the rolls are cemented together before being 
slipped over the roll, and if there is grease in the leather the 
cement will not hold. 

The preliminary tanning is done in weak bark liquor. The 
skins are then subjected to hydraulic pressure in layers be- 
tween iron plates, and are sprinkled with sawdust to remove 
the grease. They are then taken apart and paddled in a 
weak liquor, and drummed in warm salt water until all press 
creases have disappeared. 

The skins are tanned by being suspended in the liquor, 
as a smoother grain is produced in this manner than when 
a paddle or a vat is used. The liquor consists of oak bark 



232 



PRACTICAL TANNING 



extract of increasing strength, in which the skins remain 2 
or 3 weeks, when they are hung up and dried. When dry, 
they are stored away until they are to be finished. The 
longer the skins are kept in the dry condition the better they 
are when finished. 

When the leather is to be finished, the skins are sorted. 
Those that are not as perfect as they should be are finished 
into fancy leather. The roller skins are then dampened and 
shaved. The shaving must be accurate so that the skins shall 
be of even substance; however, the skins do not all have to 
be reduced to the same thickness, as some of the roller manu- 
facturers make three or four different substances. After 
shaving, the skins are drummed in sumac solution and then 





Figure 64. — Slicker and handle. Figure 65. — Moon-knife. 

go back to the tan to receive a stronger liquor. After being 
rinsed in water and drained, the skins are struck out on the 
flesh with a slicker (figure 64), and tacked out to dry. When 
dry, they are taken off the boards and softened, then trimmed 
and seasoned with milk and albumen, dried and rolled, perched 
by hand with the moon-knife (figure 65), and next re-sea- 
soned and glazed. The finished skins are then marked with a 
frame on the flesh side and trimmed with a pair of shears. 
As every hair must be removed, the skins are wiped over with 
a cotton-wool pad to find the remaining, hairs, which are re- 
moved very carefully so as not to break the grain. The skins 
are then ironed, and sorted into grades and sizes. The proc- 



VEGETABLE-TANNED LIGHT LEATHERS 233 

esses, of course, are not always followed exactly as outlined, 
but are modified as found desirable. 

Oak bark makes better roller leather than hemlock, since 
it contains less filling matter and produces lighter-colored 
skins. 

Calfskin leather: Quebracho tannage. — Calfskins for 
upper and fancy leather are tanned in numerous ways, and 
quebracho extract in solid or liquid form is in common use, 
producing a soft, tough leather. 

A practical way to tan calfskins with quebracho extract is 
carried out as follows : A quantity of the extract is dissolved 
in boiling water. Solid extract should be dissolved in a tub 
containing a false screen bottom which prevents the extract 
adhering to a solid surface. Liquid extract should be dis- 
solved in water at 180° F. The solution of extract should 
be stirred well and allowed to cool gradually before using. 
It is a mistake to chill the extract solution suddenly by run- 
ning it into cold liquor. The tannage should be started in a 
weak liquor. Having the liquor too strong, and thereby draw- 
ing the grain, must be guarded against during the entire 
process. The suspension method, by which the skins are not 
violently agitated, produces the plumpest and best tanned 
leather, especially along the sides and in the flanks. The 
skins are tacked to wooden strips with galvanized iron or cop- 
per nails, and hung in the liquor. 

The first tanning liquor is usually weak, not exceeding 10° 
bk. Where pickled skins are being tanned, salt should be 
added to the tan liquor, to prevent the acid in the skins doing 
injury. As the tanning proceeds, the strength of the liquor 
is increased until it reaches 20 to 25° bk. towards the end of 
the process. The period required to accomplish the tanning 
depends upon the" thickness of the skins, and the strength of 
the liquor. It is always advisable to tan slowly, and so get a 
fine, smooth grain. When the tanning is completed, the 
leather is washed, pressed, and fat-liquored. From 7 to 14 
days is usually required. 

Another method employs a liquor made of quebracho ex- 



234 PRACTICAL TANNING 

tract, alum, and salt for the first part of the process, and a 
clear quebracho liquor for the second part. Prepare a liquor 
by adding enough dissolved extract to water in a paddle to 
make a 40 or 50° bk. liquor, and add 1 lb. of alum and 3 
lb. of salt dissolved in hot water for every 100 gallons of 
liquor. Plunge the liquor well and throw the skins in. Start 
the wheel and turn the skins in the liquor for 36 hours or 
longer, which strikes them a light oak color; then place them 
in the second liquor, which should consist of clear quebracho 
liquor. Add enough dissolved extract to the water in the 
paddle to make a 6° bk. liquor. Turn the skins 36 hours; 
then strengthen the liquor to 10° bk., and continue the turning 
for 2 days, or as long as is necessary to complete the tanning. 
A mixture of quebracho extract and hemlock extract may be 
used in the same manner, also a mixture of hemlock and oak 
extract. 

When thoroughly tanned, the skins are horsed-up and al- 
lowed to drain several hours or over night, and are then 
placed in sumac liquor. This is prepared by adding water at 
122° F. to about 25 lb. of sumac, using the liquor at 90° F. 
The skins are thrown in and stirred more or less, and left in 
over night, then drained, set out, and either fat-liquored and 
dried, or dried without fat-liquoring. 

Gambler tannage. — Calfskins can be made into fine, soft 
leather by tanning with gambier. The skins, having been 
limed and drenched, are put into a gambier and sumac liquor 
of about 10° bk. The liquor should be slightly acid to pre- 
vent thin leather, acetic acid being used to acidify it. After 
the skins have been in this liquor from 6 to 10 hours, they are 
placed in another liquor in a paddle, made up with gambier 
to a strength of 20° bk., 1 quart of acetic acid being added for 
each 5 dozen skins. The skins remain 10 hours in this liquor. 

The third liquor should be made to a strength of 35° bk., 
and the same quantity of acid added as before. It is also 
beneficial to the quality of the leather to add, after the skins 
have been in it an hour, a pail of oak-wood extract. 

When the tannage is completed, the leather is put into a 



VEGETABLE-TANNED LIGHT LEATHERS 235 

sumac liquor for several hours or over night, then drained, 
set out, and either fat-liquored, or dried without being fat- 
liquored. The sumac gives a good bottom for the subsequent 
dyeing. 

A gambier process different from the foregoing method is 
applied in the following manner: The skins, bated and 
washed, are run in an old 12° bk. liquor until they are colored; 
and are then put into fresh gambier liquor, being hung therein 
for 12 days, during which time the liquor is gradually 
strengthened every day. The skins are then pressed and 
shaved, or split as they may require. They are next run 
in a 12° bk. liquor for a day or two before they are placed in 
a 34° bk. fresh gambier liquor for 16 days more. Salt should 
be added to the liquors to aid the tanning and keep the liquors 
from getting sour. Light skins, of course, require less tan- 
ning than heavy ones, the process described being suitable for 
heavy kangaroo skins and calfskins. 

The tanned leather is washed, set out on a machine, oiled 
or fat-liquored, and dried at a moderate temperature. When 
dry, the leather improves in texture by being kept in the 
crust some time before it is finished. It can also be passed 
through a sumac liquor after the gambier tannage is com- 
pleted. Drumming in a solution of alum and salt clears the 
grain. 

A good method of tanning is accomplished in vats or tubs 
with paddles. In the first vat the skins are colored and 
handled; in the second liquor they are tanned until they are 
ready to be skived or split; and in the third liquor they are 
tanned out after skiving. At the start, the liquor should be 
4 or 5° bk., and gradually strengthened as the tanning pro- 
ceeds, until the skins are fully tanned. Into the water in the 
vats should be put 6 or 7 pails of gambier liquor standing at 
75° Be. in the pails or stock solution, also 4 or 5 pails of sedi- 
ment gambier after the boiling. When the liquor is ready, 
put the skins in and run the paddle 30 or 40 minutes to en- 
sure good color on the grain. The liquor should be strength- 
ened twice daily — morning and evening — with 2 or 3 pails of 



236 PRACTICAL TANNING 

gambier and sediment, and the paddle run 3 times daily, 10 
or 15 minutes each time. At the end of 4 or 5 days the skins 
should be taken out of the liquor and struck out on the flesh, 
and then put into the second or stronger liquor. By running 
the paddle 3 times each day, and by adding 3 pails of 75° Be. 
gambier liquor each day, the skins become well struck through 
in about 14 days. Then set them out on the flesh side, skive 
them, and put them into the finishing liquors of 12 to 15° bk. 
for 7 days. Each day the liquor should be strengthened with 
2 pails of gambier, and the wheel run 15 minutes each time; 
one pail of salt should be added to the liquor each week. The 
final tanning can also be done in a drum. 

After the leather is fully tanned it should be cleared by 
drumming with alum and salt, oiled, and dried. It is then 
dampened, run in warm water and shaved, after which it is 
fat-liquored, set out, dried again, dampened, and colored. 

Another way to treat the skins is to wash them after tan- 
ning, then fat-liquor and dry, shave, and mill in sumac, and 
then color. Good leather is also made by giving a light fat- 
liquoring after tanning and washing, drying the skins, col- 
oring, and then giving them the second application of fat- 
liquor. 

Dongola tannage. — Gambier, alum, and salt make what is 
known as dongola leather. There are many modifications of 
this process. Fine leather is made by tanning the skins first 
in gambier or quebracho liquor, and then giving them an alum 
and salt re-tannage. For 200 average skins, a mixture is pre- 
pared of 5 lb. of alum, 9 lb. of salt, 24 lb. of flour, 10 lb. of 
egg-yolks, or a corresponding quantity of sulphonated oil, and 
8 to 10 gallons of water. The flour is made into paste with 
cold water. The alum and salt are dissolved in part of the 
water, and the flour paste is slowly stirred into the solution. 
The oil or the egg-yolk mixed with warm water is next added, 
and the whole mixture thoroughly stirred. -The tanned skins 
are drummed with this mixture one hour, then dried, colored 
and finished, thus making soft, durable leather. 

This mixture may also be used on untanned skins as they 



VEGETABLE-TANNED LIGHT LEATHERS 237 

come from the bate or drench. They should be drummed 
with it, dried, kept in crust some time, then wet-back and 
tanned with chrome liquor, the result being soft, durable 
leather. 

The combination tannage of gambier, alum, and salt can 
also be applied in the following manner: The bated and 
washed skins are placed in gambier liquor in a paddle. From 
3 to 5 lb. of gambier are used for one dozen skins. After they 
have started to absorb the gambier, from 8 to 16 oz. of alum 
and 8 oz. of salt are added to the liquor, for each dozen skins, 
and the paddling is continued until the tannage is completed, 
which takes from 18 to 36 hours. The leather is then washed 
in warm water to remove the adhering tan, next fat-liquored 
with acid fat-liquor, dried, wet-back, colored, dried again, 
and finished. After the alum and salt have been added it is 
customary to put the skins, together with the tanning liquor, 
into a drum and run them for a few hours or until thoroughly 
tanned. Some soluble oil may also be added to the liquor and 
applied to the leather toward the end of the tanning process. 
Excellent leather is also made by taking the skins out of the 
gambier liquor when they are well struck through, striking 
them out and then drumming them with a paste of water, 
flour, alum, salt, and either egg-yolk or soluble oil, drying, and 
then coloring them with a basic dye and titanium-potassium 
oxalate. 

The color of the leather can be modified by adding a solu- 
tion of fustic or other dyewood to the gambier liquor, and 
the entire process may be reversed. The skins may be first 
drummed with alum and salt and then tanned with gambier. 
Heavy skins may be tanned with gambier, split and shaved, 
and then re-tanned with gambier, alum, and salt. After the 
leather is dry, it can be colored with acid or basic dyes ; and, 
if not fat-liquored immediately after tanning, drummed with 
acid fat-liquor or with an emulsion of oil and soap, staked 
and finished. 

Velvet and suede leathers. — These leathers are produced 
from almost all kinds of skins, and there are various ways 



238 PRACTICAL TANNING 

of making them. The skins intended for this purpose are 
worked through the beam-house and tanned expressly for this 
finish, but how to get such leather out of a skin which was 
tanned in bark or some other vegetable tannage is an entirely 
different matter. The skins are sorted, and those which have 
poor grain and other imperfections are thrown aside. When 
there is enough to make a batch of 10 or 20 dozen, they are 
washed out with warm water and cleansed. The surplus 
water is then struck out, and they are snuffed on the wet wheel. 
After this has been done, they are re-tanned in a light solu- 
tion of sumac, which also acts as a mordant for the coloring. 
The skins may be colored in a tray or wheel after which they 
are fat-liquored and dried. They can be washed out, re- 
tanned, then snuffed, colored, and fat-liquored, dried, staked, 
and ironed. Care must be taken that the iron is not too hot 
or it will scorch the nap and make it shiny. If rolled in- 
stead, the skins should be rolled on the unfinished side which 
is simply to flatten them out. 

Another way is to emery the skins dry first on regular buff- 
ing wheels. Then they are treated as suggested above; but 
these skins never have such a close nap as those that are wet- 
wheeled. 

When velvet or suede leather is to be made from sumac 
or extract-tanned skins, the goods are fluffed on the flesh 
side, and the grain receives a thorough grounding or buffing 
on a buffing wheel. Another method is to stake them lightly 
and then to buff lightly on a buffing machine. At the begin- 
ning of the dyeing operations the skins are run in the paddle 
or drum for 15 minutes in lukewarm water; they are next 
treated in a weak acid bath — 0.25 per cent or less of sulphuric 
acid — and run in this for 20 minutes to clear them. The 
leather is rinsed and given a light re-tannage of 1 to 1| per 
cent of sumac extract in the drum, and is then colored. 

Russia calf. — As the skins come from the bate they should 
be in a very open and flaccid condition. They are tacked on 
sticks and suspended in the gambier liquor vats. This liquor 
is made from matt gambier to which, for each 300 lb. about 



VEGETABLE-TANNED LIGHT LEATHERS 239 

50 lb. of liquid chestnut-oak bark extract is added. The 
strength of this liquor should be about 35° bk., so that it may 
be used to strengthen the liquor in the vats or diluted for new 
liquor. The first liquor should stand at 18° bk., and should 
gradually be strengthened so that at the end of 3 days it 
should still stand at 18° bk. At the end of this time the skins 
are removed from the sticks and thrown into the first handler 
liquor. Each day thereafter they are passed forward through 
a series of stronger liquors until tanned. Calfskins usually re- 
quire 6 days in the handlers, whereas kips or heavy calf re- 
quire 8 liquors. The barkometer of the first handler should be 
about 20°, while each succeeding liquor should be slightly 
stronger until the final handler, which should stand at 30°. 
When the skins are removed from the last handler they are 
given a slight washing, pressed, and shaved, and are then re- 
turned to the yard for bleaching and re-tanning. 

Bleaching. — Either 300 calf or 150 kips are placed in the 
drum and washed for 10 minutes with running water. Twen- 
ty-five gallons of water containing 5 lb. of borax is now in- 
troduced, the drum run for 15 minutes and the skins again 
washed in running water for 20 minutes. Add 25 gallons of 
water containing 35 oz. of concentrated sulphuric acid to the 
skins in the drum, and run for 30 minutes. The stock is 
finally rinsed for 20 minutes in running water, and horsed-up 
to dry. 

Re-tanning with quebracho. — Make up a fresh quebracho 
liquor standing 8° bk. and introduce the stock — 600 calf or 
300 kips constituting a pack — run the wheel at half -hour in- 
tervals during the day, gradually raising the strength until it 
reaches 12° bk. The time of treatment should be 4 days for 
skins and about 6 days for kips. 

Drumming with sumac. — After the skins are pulled from 
the paddle they are divided into 3 packs. Each pack is 
washed with running water for 5 minutes and excess of water 
allowed to drain off. Then half fill a barrel with water, add 
32 lb. of sumac, boil, cool, and make up to 50 gallons with 
water. Mix well, and filter 25 gallons through gunny cloth 



240 PRACTICAL TANNING 

into a clean barrel. Make up the filtered liquor to 50 gallons, 
add this to the contents of the drum, run 30 minutes, wash, 
and fat-liquor. The fat-liquor should consist of a mixture 
of moellon degras, neat's foot oil and soap. They are then 
hung up to dry, given a second fat-liquoring and again dried. 

Vegetable-tanned kangaroo leather: Quebracho extract 
tannage. — In the tanning of vegetable-tanned kangaroo 
leather, quebracho extract is used, also a combination of this 
substance with gambier is sometimes employed. When que- 
bracho extract is used, the required quantity is diluted with 
water in a barrel to form a stock solution from which the tan 
liquor is made and strengthened. The first tanning liquor is 
rather weak, about 8° bk. The pickled skins are suspended 
in this liquor, which should contain some salt, and as the tan- 
ning progresses the strength of the liquor is increased until 
it is about 20°. The time required for tanning depends upon 
the thickness of the skins and the strength of the liquor, and 
ranges from 3 or 4 days to 2 weeks. Salt should be present 
in the liquor to prevent excessive plumpness of the fibers. 

A tannage with quebracho extract, salt and alum produces 
full, well-tanned leather. To every 100 gallons of quebracho 
liquor of 4° bk. strength add, while the liquor is warm, 2 lb. 
of alum and 4 lb. of salt, and plunge the liquor well. At the 
end of 36 hours the skins are ready for the second liquor. 
Heavy skins may remain in the first liquor for 48 hours. The 
second liquor consists of quebracho of 6° strength, gradually 
strengthened until the skins are tanned throughout. When taken 
from the liquor, the leather is rinsed in warm water, fat-liquored 
and dried, then moistened, shaved, colored, and finished. 

When quebracho and hemlock extracts are combined, the 
proportions should be 66 per cent of the former and 33 per 
cent of the latter. The tannage is begun in weak liquor, which 
is strengthened as tanning proceeds until the goods are tanned 
throughout. When the leather is taken out of the liquor it is 
improved by drumming in a sumac liquor for an hour or two 
before drying it out. 

Gambier and sumac tannage. — Kangaroo skins may be 



VEGETABLE-TANNED LIGHT LEATHERS 241 

struck through by being run in a paddle in gambier and sumac 
liquors of 10° bk. strength. There should be sufficient acidity 
in this liquor to keep the skins plump, they being tanned after 
bating and washing, without pickling. It is better to add a 
quart of acetic acid for 50 skins. After running in this liquor 
for a few hours, the skins are passed into a gambier liquor of 
20° bk., to which acetic acid has been added. Formic acid 
or butyric acid could be used with equally good results. 

The skins remain about 12 hours in this second liquor. The 
third liquor should be made up to a strength of 35° bk., and 
the same proportion of acid added. A small quantity of oak- 
wood extract added helps to make well-filled-out leather. 
When well struck through the skins are ready for the sumac 
bath. This is prepared in a paddle-wheel by adding water at 
125° F. to 25 lb. of best sumac and cooling down the bath to 
90° F. before putting in the goods. 

After lying in the sumac liquor over night the skins should 
be horsed-up and drained, fat-liquored, and dried ; and when 
thoroughly dry, they may be dampened, shaved, and dyed 
black. The leather should be soft and well tanned. Good 
leather is also made by tanning the goods in a liquor made up 
of 6 lb. of gambier, 2 lb. of salt, 1^ lb. of alum, 1 lb. of sodium 
sulphate, and ^ oz. of picric acid for a dozen light skins. Boil 
the gambier separately, as well as the other ingredients, and 
then mix the two solutions. The tanning liquor can be given 
to the skins in a drum, 1 gallon at a time, and drumming con- 
tinued until the goods are tanned throughout. The skins need 
not be pickled, but are tanned after bating and drenching. 
Hanging them in the liquor is also a good way to tan them. 
After being fully tanned, the leather should be drained, rinsed, 
pressed, and treated with acid fat-liquor, then dried, moist- 
ened, dyed, and finished. 

Other tannages. — Sometimes skins which have been tanned 
with gambier or with quebracho are re-tanned with alum, salt, 
and soda, then fat-liquored and dried. The entire tanning 
process can be carried out in a drum. This produces a soft 
dongola leather. 



242 PRACTICAL TANNING 

Another form of dongola tannage consists of tanning the 
skins first with gambier, then giving them a sort of kid tan- 
nage in a drum; 100 medium skins, pressed from the tan, 
being given 2 lb. of alum, 5 lb. of salt, 12 lb. of flour, 5 lb. 
of egg-yolk, \ pint of olive oil, and 6 gallons of water. The 
alum and salt are dissolved in 2 gallons of water and the flour 
is next carefully stirred in. The other ingredients are then 
mixed with warm water and thoroughly stirred in. The skins 
are drummed with the mixture until they have absorbed it, 
when they are rinsed off, struck out, and dried. 

A combination of gambier, flour, and sulphonated oil, thor- 
oughly mixed and made into a sort of paste, also makes ex- 
cellent leather. No subsequent fat-liquoring is necessary. 
One hundred medium skins free from acid require 50 lb. of 
gambier, 6 lb. of salt, 2 lb. of alum, 12 lb. of flour, 3 or 4 lb. 
of oil, and 6 gallons of water. The gambier is boiled and cooled 
and the other ingredients are added. When dry, the skins 
are dampened, shaved, dyed, dried again, staked, and finished. 

Vegetable-tanned side leather. — In the manufacture of 
leather of various kinds from hides and kips which are finished 
on the grain side, various processes of tanning are em- 
ployed. Hemlock bark and hemlock extract are used ; also gam- 
bier, chestnut and quebracho extracts, and other extracts and 
tannin-yielding materials. Quebracho extract is largely used 
alone, but it is also combined with hemlock and chestnut ex- 
tracts. Hides are also not infrequently started in quebracho 
liquor and re-tanned with some combination of extracts. Gam- 
bier is one of the staple tanning materials. It makes soft and 
tough leather which is readily colored and finished in any de- 
sired manner. The tanning with gambier and extracts is 
usually done in vats that are provided with paddles by which 
the liquor is stirred; pits or vats in which the hides are sus- 
pended are also used. The less agitation and pounding hides 
are subjected to during tanning the fuller and plumper the 
finished leather will be, especially in the flanks and along the 
sides. A common method of tanning consists of treating the 
hides with hemlock bark liquor until they are struck through, 



VEGETABLE-TANNED LIGHT LEATHERS 243 

then splitting them and re-tanning the grains with gambier 
and sumac. 

Tanning with hemlock and quebracho extracts. — One of the 
best combinations of extracts which a tanner can use is a mix- 
ture of quebracho extract and hemlock liquors. Hemlock 
is a rather harsh tannage when used alone, and quebracho is 
therefore frequently used with it, the result being soft, pliable 
leather of good color. Quebracho also hastens the tanning 
and reduces the cost. 

The hides are limed, bated and washed, and are then sub- 
jected to tan liquors, consisting of about two-thirds quebracho 
to one-third hemlock. This tannage can be used for tanning 
almost all varieties of leather. 

The color is fair and uniform, and the reduction of time 
consumed by the process is about a third of that required where 
bark liquors and "layaways" are used. The leather is readily 
colored with little or no bleaching. When hemlock bark is 
not obtainable, extract can be used in place of the bark liquor. 
The sides are first suspended in a weak coloring liquor for 
about 24 hours. They are then taken out and placed in a 
liquor of a strength of 10° bk. As the tanning progresses, 
the liquor is strengthened each day until it is about 30°. The 
tanning should not be hurried by using strong liquor, as this 
makes harsher and less desirable leather than a slower tannage 
in weak liquor. When the sides have become well struck 
through with the tan, which takes about 20 days, they are 
pressed and split. The grains are then re-tanned with hem- 
lock and quebracho liquor, or with gambier and sumac. A 
small proportion of sulphonated oil may be added to the re- 
tanning liquor with benefit to the leather. 

Tanning with quebracho extract. — This extract is used at 
present by tanners of sheepskins as well as by those of sole, 
upper, and other heavy leathers. On sides, quebracho extract 
is an admirable substitute for the higher-priced gambier, pro- 
ducing fine grain, soft texture, and firm feel. On patent 
leather it gives a pliability which prevents cracking after the 
varnish is put on. 



244 PRACTICAL TANNING 

The extract made from the wood of the quebracho tree is 
different from all other known tanning extracts, as it will not 
turn sour. In addition to this, it is a comparatively clean ex- 
tract, that is to say, it contains a higher percentage of tan to a 
given density than any other of the well-known extracts. In- 
asmuch as it has little or no tendency to ferment, quebracho 
is extremely useful for controlling the acids in tan yards, 
which tend to go sour. 

Quebracho extract, therefore, is not itself a plumper, and 
if it is used on leather which has not been properly plumped, is 
likely to tan the outside of the hides quickly and thereby pre- 
vent the penetration of the tan to the inside, the result being 
cracky leather not properly filled. If, however, hides are 
plumped before they are placed in quebracho liquor, this ma- 
terial will penetrate, fill, and produce tough, pliable stock of 
light color. 

An important point to be observed in using quebracho ex- 
tract is that it must be thoroughly dissolved. Solid extract 
should be boiled in a tub containing a false screen bottom, 
which prevents its adhering to a solid surface. The liquid 
extract should be dissolved in water at 180° F. The result- 
ing solutions from both grades of extract should then be 
stirred well and allowed to cool down gradually before being 
used. It is a great mistake to run hot quebracho liquor into 
cold vat liquors, or in fact to chill any extract liquor suddenly. 
The sediment that remains in the cooling tub may be worked 
up with fresh water on a tail leach or elsewhere. A great 
deal of the successful use of quebracho in the vats depends 
upon the proper method of dissolving it, and it is much better 
that such precipitation as takes place should go on in the cool- 
ing tub rather than on the leather. 

Tanning with gambier, sumac, and oak extract. — Where a 
soft well-tanned leather is required, which can be colored any 
shade or dyed black, a tannage with gambier, sumac and oak 
extract may be used with satisfactory results. The hides 
should preferably be split out of the lime and the grains then 
bated and washed. A liquor composed of gambier and sumac 



VEGETABLE-TANNED LIGHT LEATHERS 245 

of about 10° bk. is prepared in a paddle. After the grains 
have been in this liquor for 5 or 6 hours, they are put into a 
gambier liquor of 20°, to which a quart of acetic acid for 
40 small grains has been added. Tanning may be accom- 
plished by suspending the goods in the liquor, by using a pad- 
dle or by drumming after the grains have been well struck 
with the tan. 

The third liquor should be made up to a strength of 35° 
bk., and the same proportion of acid added. After the grains 
have been in this liquor for 3 hours, a few pails of oak-wood 
extract should be dissolved and added. The tanning should 
continue until the goods are tanned throughout. When this 
has been accomplished, the leather is drained and then treated 
with sumac in a drum or a paddle. 

A sumac liquor is made up in a paddle by using 25 lb. of 
best sumac in water heated to 125° F., the liquor being cooled 
down to 90° F. before the skins are put in. The leather may 
be turned in this liquor several times and left in over night, 
or drummed with it two hours ; it is then drained, rinsed off 
and dried or fat-liquored, dried, colored, dried again and 
finished. 

Equally good results may be obtained by using quebracho 
extract in place of gambier. In the last stages of tanning, 
if a drum is used, some sulphonated oil may be added to the 
liquor. This helps in getting leather dried soft and pliable, 
and reduces the amount of fat-liquor to be given later on. 
The sumac for one dozen sides may be made from 2 pails of 
sumac scalded in 20 gallons of water, and used at 90° F. The 
leather may be drummed in the liquor 2 hours, piled down 24 
hours, drummed again 2 hours, rinsed off, and dried. 

Tanning with gambier. — The sides are started in weak 
liquor, which is gradually strengthened by the addition of 
fresh gambier until it becomes fairly strong towards the end 
of the process. Common salt serves a useful purpose in 
gambier tanning, as it assists in making soft leather, in has- 
tening the tannage, and preventing contraction of the leather 
fibers. Acetic acid also should be added to gambier liquor 



246 



PRACTICAL TANNING 



to prevent thin, papery leather. It is well for the tanner to 
divide his tanning liquors into three portions : In the first 
the hides are colored ; in the second the tanning goes forward 
until the leather is ready for splitting; and in the third the 
re-tanning after splitting is accomplished. At the beginning 




Figure 66. — Union splitter. Formerly much used for furniture and 
automobile leather, but now replaced by band-knife machine. 

the liquor may be 4 or 5° bk. It should be strengthened twice 
each day, the quantity of fresh liquor added depending upon 
the size of the vats and the strength of the liquor at the start. 
No exact rule can be laid down, as the individual tanner must 
decide this and other problems. The tanning should always 
go steadily forward until the hides are tanned throughout, 
when the leather should be split, re-tanned, and fat-liquored. 
Combination process. — A tanning process in which hem- 
lock, chestnut wood, and quebracho extracts are used for 



VEGETABLE-TANNED LIGHT LEATHERS 247 

tanning, and quebracho and gambier for re-tanning, is car- 
ried out in the following manner: The hides are hung on 
sticks in a 7° bk. hemlock liquor, and are handled each day 
for 3 days, the liquor being strengthened up to 10°, and finally 
up to 12°. After having been in the 12° liquor 24 hours, the 
sides are passed into a 16° combination liquor, made of chest- 
nut-wood extract and quebracho extract. This liquor is grad- 
ually raised to 20°, the process requiring from 14 to 16 days. 
The sides are then pressed, split, and tanned. The re-tanning 
liquor is made of quebracho extract and gambier, 3 parts of 
the former and 1 part of the latter; and the strength 26° bk. 
The grains are drummed an hour in this liquor, then left in 
piles 24 hours; drummed again for an hour; piled down for 
24 hours; then washed and finished. This is a good tan- 
nage for many varieties of leather, shoe upper, bag, case, etc. 
As described, it is most suitable for large, heavy hides. 

Pressing and splitting. — Before leather is split it is pressed 
to rid it of surplus liquor and to put it into good condition for 
splitting, which may be done on the union splitter (figure 
66) or on the belt-knife machine. Considerable moisture 
should, however, be left in it. When pressed too dry, the 
leather must be milled with weak liquor to prepare it for the 
strong re-tan liquor, and this milling pounds the grain and 
makes it loose and "pip e Y-" 

When there is considerable moisture in the grains they do 
not need to be milled in weak liquor, but can be put at once 
into the re-tan liquor. The more moisture there is in the 
grains the better the results. 

Re-tanning with gambier and sumac. — Leather that has 
been tanned in hemlock liquors, no matter what the finish may 
be, is much improved by being re-tanned with gambier and 
sumac. Re-tanned in this way, the flanks are made fuller and 
firmer, the fibers are slightly contracted, the harsh effect of the 
hemlock is toned down, the leather is given a smooth feel, and 
the color is less liable to fade. The leather is tanned with 
hemlock and then split. 

The re-tanning is effected in a drum, being thus accom- 



248 PRACTICAL TANNING 

plished in less time than in a vat. A good re-tanning liquor 
for harness and other kinds of leather is prepared in the fol- 
lowing manner : Boil 250 lb. of gambier in 80 gallons of water ; 
and when the solution is fairly cool, skim off all foreign 
matter. Ten gallons of this liquor is sufficient for 30 aver- 
age sides. This quantity is put into the drum, together with 
the leather, and 2 gallons of dry sumac are added and as much 
water as needed to make the leather wet without dripping. 
Run the leather in this liquor at least 30 minutes. The sides 
should then be packed in boxes by doubling the flesh side out- 
ward, and left in that condition for 10 or 12 hours. 

They should next be scoured or washed, and treated in the 
usual way of coloring, fat-liquoring, etc., according to the 
kind of leather and the finish desired. Gambier and sumac 
used as described improve the leather greatly, and the expense 
of their use is repaid by the improved quality. Bark-tanned 
and extract-tanned leather may be re-tanned with gambier and 
sumac in the following manner : Two pails of Sicilian sumac 
are boiled 15 minutes in 40 gallons of water, and the resulting 
liquor is allowed to stand over night. On the next day, 12| lb. 
of gambier is boiled until dissolved, and this solution, together 
with 10 lb. of salt, is added to the sumac liquor. There 
should be 50 gallons of the liquor, and it should be used at 
80° F. The leather is run in it one hour, then left in piles 
24 hours, rinsed off, and fat-liquored. Before being re-tanned, 
the leather, after it has been split and shaved, should be 
washed for a half -hour in warm water containing 3 lb. of po- 
tassium carbonate in 50 gallons of water. It is next drained 
and washed, and then re-tanned. 

Re-tanning grains with sumac. — Hemlock-tanned and com- 
bination-tanned leather, after it has been split into grains and 
splits, is benefited by a re-tannage with sumac. The sides are 
taken out of the last tan liquor and allowed to lie in a pile 
48 hours. They are then pressed or put through a wringer 
to force out the surplus liquor. Some tanners run their leather 
through a splitting machine with a corrugated gauge • roll, 



VEGETABLE-TANNED LIGHT LEATHERS 249 

which makes pressing unnecessary. Leather that has been 
pressed usually shows some marks, and to remove these it is 
jacked on a stoning-jack (figure 67). 

Splitting is the next operation, and the grains are then re- 




Figure 67. — Iron frame stoning-jack. 

tanned with sumac in a drum. This re-tanning is very bene- 
ficial to the leather, making it of finer texture and color, also 
rendering it capable of taking better and more uniform 
coloring. 

The sumac liquor is prepared by scalding 2 pails of sumac 
with 20 gallons of water heated to 125° F., and allowing it 
to steep some time before using it. When the liquor is cool 
it is ready for use, this quantity being sufficient for one dozen 
medium sides. The leather is drummed an hour in this liquor. 
It is then placed in smooth piles for 24 hours, when it is 
drummed again with sumac liquor the same as before, then 
again piled down for 24 hours. The next operation is dip- 
ping the leather in warm water to wash off the sumac, and 
then scouring or setting it out and finishing it according to 
the finish desired. It can be dried and then fat-liquored later. 



250 PRACTICAL TANNING 

The splits for flexibles or Goodyears are trimmed and put 
into a drum, together with tan liquor of 6° bk. strength, and 
drummed one hour, which opens them so that they will take 
the re-tanning liquor. Re-tanning can be done in a drum in 
about 6 days, the splits being drummed in a strong liquor 2 
hours each day and left in piles the remainder of the time. 
This operation is repeated daily for 6 days, when the splits 
will be fully tanned and in better condition than when they 
are drummed continuously. 

Gambier, hemlock extract, and alum make a good re-tan- 
nage for hemlock-tanned leather. The proportions of gam- 
bier and hemlock should be equal parts of each, the strength 
being 25° bk. Twenty-five sides should be given 4 pails of 
the liquor and 4 lb. of alum dissolved in 2 gallons of water. 
The leather is run with this liquor for an hour, then piled 
down over night and hung up the next morning to dry. When 
dry, it is fat-liquored, colored, and finished. 

A combination of 75 per cent of quebracho and 25 per 
cent of gambier is recommended for re-tanning grains for 
upper leather. One pint of sodium bisulphite added to each 
3 gallons of re-tanning liquor causes the liquor to penetrate 
more quickly into the leather. The strength of the quebracho- 
gambier liquor should be from 24 to 28° barkometer. 

Any of the foregoing processes may be used in the re- 
tanning of leather for colored and black upper stock, dull 
or bright grains, and imitation kangaroo; also for bag and 
case leathers. 

Tanning sealskins. — Raw sealskins come to the tanner in' 
a freshly salted condition, and are, broadly speaking, divided 
into two classes : "small" or "white-coat seal" and "large" or 
"cow seal." 

The former seals are principally used for making levant 
grain leather, and the latter for walrus grain, though a grain 
similar to the latter is frequently produced on the small seal 
and likewise the levant grain on cow seals. As the processes 
differ somewhat in obtaining the different grains, it is neces- 
sary to describe them separately. 



VEGETABLE-TANNED LIGHT LEATHERS 251 

Levant grain. — The skins, when received by the tanner, are 
covered with salt and are very greasy. A convenient pack 
of about 25 dozen is placed in the soak pits. The water in 
the pits should not be too cold, and during the winter there- 
fore it is necessary to warm it a little. 

After remaining in soak for a day, the pack is hauled-up 
and fleshed over a beam. As much of the loose blubber and 
grease as possible is removed by the beamster. The skins are 
then put into a fresh soak and remain in it 48 hours, when 
they are again scraped over the beam, this time on both flesh 
and hair sides. It will be found, owing to the greasy nature 
of seals, that the beamsters have difficulty in handling their 
knives, but this is readily overcome by occasionally rubbing 
their hands with sawdust. 

The skins are now ready for liming. White lime alone 
should be used, as it has been found to produce the best re- 
sults. Sodium sulphide and lime produces pipey grain, but 
arsenic and lime yields a soft and silky grain. 

The time required for liming varies according to the 
weather, in winter 21 days being needed, while in summer 
not more than 16 days are required. The extremely greasy 
nature of the skins make it necessary to give them this long- 
liming. To produce a' firm leather with the requisite hard 
grain it is necessary to keep the limes as fresh as possible ; old 
and stale limes make leather which is tender and has a soft 
grain. 

The skins are unhaired on the beam; care being taken to 

.rid them of the young hair, which is sometimes difficult. After 

unhairing, the superfluous lime is removed by washing in a 

wheel. When the water running off is quite clear the skins 

are ready for puering or bating. 

Good results are obtained with Dennis "puerine," or with 
oropon. The skins should be brought down fairly low, and 
a good guide to determine when they are low enough is to 
take one out occasionally and pinch it between the forefinger 
and thumb. The process has gone far enough when a de- 
cided impression is left on the grain. From 2 to 6 hours 



252 PRACTICAL TANNING 

should bring them down, though large skins require longer 
treatment. The skins are next scudded over a beam, slate 
knives being usually used for this, which is an important 
operation as it removes any free lime or lime salts in the skins. 

After scudding, the skins should be thrown into a bran 
drench and left in for 5 or 6 hours. They are then rinsed 
in warm water and tanned. 

Quebracho extract and sumac are employed for tanning the 
skins. A cube of solid quebracho extract is dissolved in a 
barrel of boiling water. This constitutes a stock solution. 
A 10° bk. solution of this extract is taken and drummed, to- 
gether with the skins, in a closed wheel for an hour, sufficient 
liquor being used to cover the goods. This sets the grain. 
The skins are then put into a paddle containing about a 12° 
liquor, and remain in it until they are tanned, the strength of 
the liquor being gradually increased. Tanning should be com- 
pleted in a week, which can be tested by cutting off a small 
piece and observing whether the tan liquor has entirely pene- 
trated the middle of the skin, leaving no white streak. When 
tanned, the skins are drummed for 2 or 3 hours with a liquor 
made of a half bag of sumac and a few pails of liquor. They 
are then struck out on a machine and hung up to dry. When 
quite dry, they are taken down and struck out either by hand 
or by machine, using hot water to soak them in; then they 
are hung up for part drying. Such edges as dry out 
should be re-dampened with a sponge before re-setting the 
skins on a table. After this re-setting, the skins are ready 
for blacking. 

Walrus grain seal. — The large sealskins generally used for 
this kind of work are soaked in the manner already described. 
In liming them, however, a pound or two, according to the 
size of the pack, of sodium sulphide is used with lime. From 
10 to 16 days is enough liming for this class of work. 

When unhaired, the skins are washed in water and bated ; 
then taken out and drummed in warm and fairly strong liquor, 
which contracts the grain, thus forming the well-known walrus 
grain. The subsequent tanning is effected in a paddle, and 



VEGETABLE-TANNED LIGHT LEATHERS 253 

when tanned, the skins are hung up, dried, blackened, grained, 
and seasoned. 

Heavy skins are split out of the lime on a belt-knife ma- 
chine. The substance of the grains and splits varies accord- 
ing to the requirements of the market. The grains are fin- 
ished into patent or enameled leather, and also for bookbind- 
ings and fancy leather goods. Two thin middle splits and 
one rough split can, as a rule, be made from each skin; and 
the "linings" are then usually thrown back into the limes for 
about two days, with one handling, to get rid of as much 
of the grease as possible. The linings are then washed in tepid 
water, slightly acidified with acetic acid to neutralize any 
hardness. 

The split skins are bated, drenched, and slated out of warm 
water, and are then ready for tanning. 

In addition to the process of tanning with quebracho and 
sumac, already described, sealskins may be made into good 
leather by tanning with gambier and sumac, the liquor at the 
beginning being about 10° bk. strength. Care must be taken 
to have plenty of acid, otherwise the skins will fall, and will 
be flat and papery when finished. After running in this weak 
liquor for about 6 hours, the skins are passed into a 20° liquor. 
It is well to add about a quart of acetic acid for every 5 dozen 
grains or linings. The goods remain in this liquor about 7 
hours. 

The third liquor should be made up to a strength of 35° 
bk., and about the same amount of acid mentioned above 
should be added. It will also help to fill out and improve the 
goods if a pail of oak-wood extract is added to the liquor after 
the skins have been running in it half an hour. If this has 
been properly carried out, the goods will be struck through, 
and should be horsed-up and allowed to drain ready for 
sumacking. 

This is best done in a vat, although a paddle is sometimes 
used. This bath is prepared by adding water at about 125° 
F. to about 23 lb. of best Palermo sumac. Cool down to 
86° F. ; enter the goods and haul-up once or twice, warming 



254 PRACTICAL TANNING 

the liquor each time. After lying in the sumac over night 
the skins should be horsed-up, and, after draining, taken to 
the sheds for drying. Care should be taken not to expose 
them to strong or harsh winds in the early stages, and the 
use of steam and artificial heat should be avoided as much 
as possible. 

Tanning the splits. — The splits may be tanned as follows : 
Put them in a mixture of best oak-wood extract and water 
at 35° bk., and for every 5 dozen splits add 2 quarts of acetic 
acid, which helps to maintain the goods in a plump condition. 
Keep the splits (linings) in this liquor for two days, handling 
once. Horse-up to drain and dry out steadily. Cube gam- 
bier costs more than block gambier, but it is richer in tannin 
and does not contain dross. The best Sicilian sumac should 
always be used. 

Directions for finishing. — When the grains are brought 
down from the shed, they are treated, where weight is a con- 
sideration, as follows : For every 10 dozen take 28 lb. of 
barium chloride, and with sufficient water to wet them, work 
the goods in a drum, together with 6 gallons of sumac for an 
hour at 104° F. From this they are plunged, a dozen at a 
time, into a weak solution of sulphuric acid, which should be 
moderately acid. Stir the skins for 3 or 4 minutes until they 
assume a whitish appearance. The chemical action causes the 
barium chloride to be changed into barium sulphate. After 
each dozen skins is taken out of the bath, sufficient acid should 
be added to maintain the required acidity. 

The skins are now ready for hoisting up and striking up, 
the latter being done on the grain side in the ordinarv way, 
and the grain wiped over with best linseed oil. They are then 
hung up to stififen sufficiently for setting. When ready, let 
them lie in piles, after damping down all dry parts, for a day 
or two, and then set out lengthwise and after that from neck 
to butt. Now hang them up and allow them to dry out. When 
dry, break down with the graining board (figure 68), push- 
ing the goods upon the flesh side from neck to butt, and turn- 
ing and doing the same on the grain side. Fluffing or buffing 



VEGETABLE-TANNED LIGHT LEATHERS 255 

follows. This should be effected on a fine emery wheel, and 
done crossways, commencing at the butt, going about half 
across, turning round and reversing; then drawing the skins 
straight down on the grain. 

Treatment for split linings. — The linings, after being dried 
out, may be weighted by drawing them through a strong solu- 
tion of barium chloride, as above described, but they must be 
drawn through the acid bath one at a time, if tearing is to be 
avoided. Now wash them with warm water and lightly strike 
out with a suitable ridging board. The splits are then ready 




Figure 68. — Cork arm-board. 

for staining, and, when dry, are buffed on one side and enam- 
eled on the other. 

Tanning pigskins. — Pigskins usually come to the tanner 
in a pickled condition, and should be de-greased by running 
in lime or soda solution. They may be also very satisfactor- 
ily de-greased with the gargoyle compound, described in 
Chapter II. 

Quebracho extract makes a satisfactory tannage for pig- 
skins. Prepare a liquor by adding enough dissolved extract 
to 700 gallons of water in a paddle to make a 4° bk. liquor. 
To this liquor add 10 lb. of alum and 25 lb. of salt dissolved 
in hot water. Plunge the liquor until it is thoroughly mixed. 
Start the wheel, throw in the skins, and turn them 36 hours 
or longer, which strikes them a light oak color, and they may 
then be placed in the second bath, which should consist of 
clear quebracho liquor. 'Add enough dissolved extract to 
the water in the paddle to make a 6° liquor, omitting the alum 
and salt. Turn the skins 36 hours ; then strengthen the liquor 



256 PRACTICAL TANNING 

to 10°, and leave the skins in the liquor for two days, which 
completes the tanning. The second liquor may also be given 
the skins in a drum. A mixture of quebracho and hemlock 
extracts may be used; also a mixture of hemlock and oak 
extracts. 

When the skins are tanned, pass them into a sumac liquor 
in a paddle or vat. The liquor is prepared by adding water 
at 122° F. to 25 lb. of sumac. Cool down to 86° F. before 
entering the goods, and haul-up once or twice, warming the 
liquor each time. After being in the sumac liquor over night 
the skins are struck out and oiled on the grain with neat's foot 
oil or sulphonated oil, and hung up to dry or tacked on 
frames. When dry, they are staked and boarded, and are 
then ready for the finish. The leather can be bleached if a 
lighter color is wanted, or colored any shade, or dyed black. 

Quebracho makes a fine, natural grain, free from spue, and 
firm, strong leather. For bag leather, hemlock extract is a 
good tannage; so is hemlock and quebracho. The skins are 
started in a weak liquor, which is strengthened twice a day, 
until they are struck through, which takes about 8 days. After 
tanning, they may be bleached and drummed in a sumac bath. 
Next wash them with clean water; slick them out; give them 
a little oil and hang them up to dry. After drying, dampen 
and shave the skins that need it and then apply fat-liquor. 

Tanning with sumac, oak bark, and alum. — A soft, light- 
colored pigskin can be produced by tanning in the following 
manner : Pickle the skins with sulphuric acid and sodium chlor- 
ide (salt) ; next remove the acid in a drench of whiting and 
salt, and then wash them in two baths of warm salt water. 
To make the tan liquor, dissolve 6 lb. of alum, 4 lb. of Glaub- 
er's salt, and 4 lb. of common salt in 6 gallons of water; in 
another tub boil 5 lb. of ground sumac, 3 lb. of oak bark, and 
1 lb. of ground nutgalls in 5 gallons of water. Mix the two 
solutions ; strain the mixture while it is hot, and add 4 oz. of 
sulphuric acid. The liquor should be used lukewarm, and the 
skins drummed in it for several hours, then allowed to drain 
24 hours. Tanning can also be effected in a paddle. 



VEGETABLE-TANNED LIGHT LEATHERS 257 

After draining, the skins should be struck-out on both sides 
and oiled fairly heavily and dried. As they dry they should 
be staked, so that when the leather is dry it is soft and pli- 
able. It can be easily colored any shade. It is quite water- 
proof and durable. Oak bark is an especially good tannage 
for pigskins ; so is chestnut extract. 

Another method of tanning with quebracho and sumac is 
carried out as follows : A cube of solid quebracho extract is 
dissolved in a barrel of boiling water, forming a stock solu- 
tion. A 10° bk. solution of this extract is taken and drummed, 
together with the skins, in a closed drum for a half-hour or 
longer. This sets the grain. The skins are then put into 
a paddle containing a 12° liquor, and remain in it until they 
are tanned. The strength of the liquor is gradually increased. 
When tanned, the skins are drummed with sumac liquor for 
2 or 3 hours ; they are then struck-out on a machine and hung 
up to dry. For black leather the skins may be handled and 
blacked in the same manner as sealskins. 

Tanning snake skins. — These skins should be soaked until 
soft, then limed to remove the scales; and after bating they 
may be tanned in bark or extract liquors like calfskins and 
sheepskins, beginning with weak liquor, handling often, and 
increasing the strength daily. While soaking, they should be 
worked by hand until they are soft and flexible and the outer 
scales have been removed ; they are then in condition for tan- 
ning. Gambier, sumac, quebracho, chestnut extract, or a 
combination liquor may be used. The tanned skin is soft and 
flexible, and the natural colors are little changed. 

A process of tanning with alum, salt, and gambier is car- 
ried out in the following manner : The skin is soaked in the 
usual way. It is then fleshed and put into lime for 4 or 5 
days until the outer scales can be removed. It is then bran 
drenched and depleted, washed, and pickled for 2 days with 
salt and alum liquor of 1 part alum, 2 parts salt, and suf- 
ficient water to cover. Tanning is then started in a 5 per 
cent gambier liquor, which is strengthened daily until it 
reaches 10 per cent. The skins are tanned in a few days. 



258 PRACTICAL TANNING 

Quebracho extract or chestnut extract may be used in the 
same manner as gambier. After the tanning is completed, the 
skins are fat-liquored with sulphonated oil ; dried, wet down, 
shaved, sumacked, oiled again if necessary, stretched out 
carefully, and dried. The flesh may be made clean and smooth 
with sandpaper or on an emery wheel. A bright finish is 
obtained with casein or shellac; a dull finish with flaxseed 
liquor or gum tragacanth. 

Fancy leather calfskins. — Only the finest calfskins are 
selected for this class of leather, and they should, as far as 
possible, be free from butcher cuts and other imperfections. 
The weight of the skins for this line of manufacture usually 
runs from 4 to 7 pounds each. They are generally green- 
salted or are in a dry-salted condition, and must be soaked 
in water in the usual manner, and made soft and clean. 

One hundred skins make a pack of convenient size. They 
are first run in a drum which permits a constant supply of 
water being run into it while revolving, and which has open- 
ings for the water to run out again. If the pack is green- 
salted, washing for one or two hours is sufficient; but dry- 
salted stock requires longer treatment. The main object is 
to get the skins soft without the loss of substance, and this 
can be greatly accelerated by having pegs inserted in the inner 
side of the drum. The skins are next fleshed and limed. 

During the liming of this class of leather, the tanner must 
remember that a very soft-finished product is required, with 
a tight, smooth, and clear grain ; therefore great care k and 
judgment must be exercised at this stage, for, as most tanners 
know, the liming makes or mars the finished product. Local 
conditions must be considered, as well as the season of the 
year. 

Lime and arsenic are the depilatories used. The arsenic 
is valuable, not only in hastening the loosening of the hair, 
but also for the softening effect it has upon the skins, ren- 
dering them supple and making the grain close and smooth. 
After remaining in this one or two days, they are hauled up 
and allowed to drain, preparatory to going into new lime. 



VEGETABLE-TANNED LIGHT LEATHERS 259 

After unhairing, the skins are well washed in running water 
until the surface lime is removed and then bated and de- 
limed. This is done in one of the several bating processes 
which have been described for calfskins, the method of bat- 
ing with oropon, or the process in which glucose, sulphur, 
and yeast are used, being especially suitable. The skins should 
be bated in such a manner that they are soft and clean, and 
have the fine grain that is desired. After having been bated 
they are scudded. This is done on a bolstered beam, using 
a slate knife, and is an important operation, as it removes 
much of the dirt and rids the skins of lime dissolved by the 
bate. Furthermore, all of the fine hair which may still be 
in the skins is removed. The skins are next drenched with 
boracic acid, formic acid, or any other suitable drenching ma- 
terial, and are then pickled. 

Pickling for this class of leather is effected satisfactorily 
with formic acid and salt, which cleanses the skins and gives 
them a good grain. Pickling makes soft leather which has 
a clear grain and good color. Quebracho extract is commonly 
used for tanning skins for fancy leather. Some of this is dis- 
solved by boiling in water in a barrel, thus forming a stock 
solution from which the tan liquors are made up and strength- 
ened. The skins are held in suspension in the vats by tack- 
ing them to wooden strips, using galvanized iron or copper 
nails so as not to stain them. One nail on each butt shank is 
enough, two skins on each side of the strip, with the grain 
side out, being thus suspended. 

The first liquor in which the skins are hung is weak, from 7 
to 10° bk. As the tanning progresses its strength is increased, 
so that at the last it will be of 20 to 25°. The chief point 
to be considered is to avoid drawing the grain by using too 
strong liquors at first. Salt must always be present, especially 
when sulphuric acid is used as a pickle, to prevent injury 
from the acid. The time required for tanning varies accord- 
ing to the handling of the skins and the strength of liquors, 
but should be accomplished in 7 to 14 days. 

When the tanning is completed, the skins should receive a 



260 PRACTICAL TANNING 

slight fat-liquoring. The grease should be entirely absorbed 
by the leather; the skins are then drained, slightly struck-out 
on the flesh side, or hung up at once and dried. When thor- 
oughly dry they are sorted into various grades; those that 
are light in color, clear of grain, and free of imperfections 
being put into the lightest colors, while those with slightly 
imperfect grains are most suitable for black leather. 

Combined vegetable and mineral tannage. — Each of 
these two methods of tanning possesses unique advantages, 
and it has been the aim of tanners to incorporate them into 
one method, but so far this has not met with much success. 

The chrome process gives, for example, suppleness and 
toughness to leather without fullness or weight, so that any 
skin that has been chrome-tanned must not be inclined to 
looseness of texture, as this fault would be accentuated in the 
finished leather. The vegetable tanning process, on the other 
hand, gives excellent weight and fullness, but lacks the char- 
acteristic suppleness and strength of chrome leather. When 
a combination of these two processes is tried by making one 
follow the other, it is usually found that the production of 
one good quality is accompanied by the presence of a corre- 
sponding bad quality. For example, if empty chrome-tanned 
leather is, for the sake of fullness and firmness, re-tanned in 
some vegetable tanning liquor, these two qualities will be pro- 
duced, but the toughness of the leather will be sacrificed. 

Vegetable-tanned patent shoe tipping. — The tanner who 
makes chrome leather from hides can realize greater profit 
from his poor-grained hides by working them into tipping 
stock than by allowing them to go through the works, and 
then to be sold as No. 3 chrome or as a job lot of culls. 

Good, strong tipping requires more liming than chrome 
leather. If the tanner will sort his hides after they are de- 
haired, he can have an extra lime pit and make up a medium 
strong lime liquor, and all hides with damaged grain can be 
put into this lime for 24 to 48 hours, and then be put through 
the regular system of washing, working out, bating, etc. 
After having been bated down well (tipping stock should be 



VEGETABLE-TANNED LIGHT LEATHERS 261 

bated low, to make a soft, strong leather), the hides should 
be started to tan by tacking them on sticks and suspending 
them in a weak sour liquor. If a non-acid tanning agent is 
being used, the liquor should be turned to the acid side by 
the use of lactic acid. The first liquor should stand about 7° 
test with a barkometer. Allow the hides to remain in this 
sour liquor for 48 hours, then handle them over into another 
pit, or else draw off the sour liquor and pump on a fresh 
sweet liquor of 10° strength. If handled over into the next 
pit, the hides should be pulled out and laid in a pile to drain 
for two hours in order that they will not carry too much of 
the sour liquor into the next pit. Allow them to remain in 
the 10° liquor 48 hours, then work them into a 12° liquor for 
48 hours. Next work them into a 16° liquor and allow them 
to remain 4 days, but they must be handled each day and their 
positions changed, so that they will not have raw or "kissed" 
spots on them. After having been in the 16° liquor the re- 
quired period, the hides are worked out into a 20° liquor and 
allowed to stay therein 6 days, when they are pulled down 
from the sticks and allowed to lie in a pile 48 hours. They 
are then pressed or put through a wringer so that they will be 
in condition for splitting, or they can be run through a split- 
ting machine with a corrugated roll without pressing or wring- 
ing. If pressed or put through a wringer, they must be 
jacked on a stoning-jack to remove all marks. 

After having been jacked, they are split at a 2\ oz. gauge, 
and the grains are then re-tanned in a mill with sumac, using 
two pails of sumac to each dozen sides. Boil the sumac in 
about 20 gallons of water, and allow it to stand until cool, 
then put in the leather and run 1^ hours, take the leather out 
and put it into a pile for 24 hours; then give it another run 
in sumac liquor made in the same way. The leather is piled 
down again and allowed to rest for 24 hours. It is then 
dipped into a tub of warm water to wash off the sumac, and 
after that is scoured on the table. While on the table, give 
the leather a good coat of moellon degras, made by dissolving 
4 oz. of potassium carbonate in 3 gallons of hot water and 



262 PRACTICAL TANNING 

then stirring in 2 gallons of the degras. The leather is given 
a light coat of this slush, well rubbed in with a brush. It 
is now folded together and laid in a pile for 24 hours, then 
tacked out on frames. When dry, it is buffed by hand, and 
either staked or soft-boarded and pin-blocked to soften, when 
it is ready to japan. De-greasing is unnecessary when a first- 
class moellon degras is used. 

'Another re-tanning process. — A good way to fit bark-tanned 
leather for patent shoe tipping is to split and shave it on the 
machine, then for 50 medium sides dissolve 3 lb. of potassium 
carbonate in 50 gallons of warm water and run in a mill for 
a half-hour, then drain and wash for 15 minutes, when the 
leather will be in good condition to be re-tanned. 

The re-tanning liquor is made as follows : Boil 2 pails 
of sumac in 40 gallons of water for 10 minutes, and allow to 
stand over night. In the morning dissolve 13 lb. of gambier 
and 10 lb. of salt and add the solution to the sumac liquor. 
There should be 50 gallons of liquor. Run the sides in this 
liquor one hour, using it at 80° F. ; next pile them down on 
the floor for 12 to 24 hours, and then wash off the sumac in 
a tub of water. 



CHAPTER IX 
VEGETABLE-TANNED SOLE LEATHERS 

Rapid tanning processes. — In modern plants, sole leather 
is tanned in hangers and layaways, and then made plump and 
solid by being drummed in strong liquor made from que- 
bracho or bark extract. As the drum revolves, the extract is 
forced into the leather, which absorbs the condensed tanning 
■ material in a few hours. Before this is done, however, the 
leather, already fairly well-tanned, is run through the wring- 
ing machine and the surplus liquor is forced out. 

Some tanners use whole hides, and by having plenty of 
liquor in the drum, get good, smooth grain on their leather. 
The grain should be well set before the drumming in ex- 
tract is begun. The extract is mixed with sweet liquor heated 
to 80° F. ; it is also used in liquid form as taken from the 
tank or barrel The leather, when the drumming is com- 
pleted, is removed from the drum and placed in warm water 
for a few hours, which plumps it; it is then oiled, dried, 
sammied, and rolled once or twice. When the preliminary 
tanning is done properly, the finished leather is well-tanned, 
plump, solid, and has good weight. Quebracho extract in 
concentrated form is the material usually preferred for the 
drumming process. Apparently firm and solid leather is ob- 
tained by using glucose, which makes plump flanks, bellies 
and shoulders ; but the plumpness and solidity thus acquired 
are not real, and the leather does not give satisfaction. 

The only way to make durable sole leather is by using 
nothing but vegetable tanning extracts. Some tanners, after 
the drumming in extract is completed, hang the leather in 
strong liquor made from the extracts from the drum ; then 
they bleach it with acid and soda; oil it and hang it up to 
dry in a well ventilated but darkened room; and then roll it 

263 



264. PRACTICAL TANNING 

for market. A mixture of equal parts mineral oil and cod oil 
is often used for oiling sole leather. Soluble or sulphonated 
oil is also drummed into the leather and adds to its pliability 
and strength. When the drum process of tanning is used, 
it is the practice of some tanners to send the old drum liquors 
to the handlers. These drum liquors are entirely sweet, and 
do not contain enough free acid to plump the hides properly 
while they are in the handlers; hence it is necessary to add 
lactic acid to the liquor in order that there may be the requisite 
proportion of acid to plump the hides. Not only is it advis- 
able to add the acid to the head-handler liquor, but also .to 
the handlers half-way down the series, in quantities growing 
smaller from the head liquor. The green hides are given a 
week in the handlers; next they go through a roller press or 
a wringer, and are then ready for the drumming process. 
During the latter process, the two essentials are the mainten- 
ance of the strength of the liquor, and keeping the leather 
comparatively cool. When the hides are found to be heating, 
they should be allowed to cool off before proceeding with 
the drumming, and the old liquor run to the handlers and 
fresh liquor supplied to the hides. 

Neutralizing the lime in the hides by hanging them over 
night in cold water containing lactic acid, which also plumps 
them before putting them into the handlers, considerably short- 
ens the period they have to remain in the handlers. Tan 
liquors at this time usually contain too little acid to neutralize 
the lime and keep the hides plump, and some process of de- 
liming is necessary. Lactic and acetic acids are commonly 
used in tan liquors. Butyric acid also is used for de-liming, 
and is an excellent plumping acid for the early tan liquors. 
Some tanners drench their hides with boracic acid, which not 
only removes the lime, but also gives the grain a smooth, silky 
feel and appearance. 

Some tanning extracts are more astringent than others, and 
when several tanning materials are being employed it is best 
to use the less astringent materials during the first or earlier 
stages of tanning, and use rockers so that the hides can 



VEGETABLE-TANNED SOLE LEATHERS 265 

be kept in motion and penetration by the liquor facilitated. 
The earlier liquors fix the grain and give it good color, and 
they should be weak. When the grain is colored and set, the 
hides are in condition to receive stronger liquors. The 
strength of tanning liquors should be increased rather slowly 
to prevent thickening the grain and a wrinkled or drawn ap- 
pearance. When strong liquor is used during the early stages 
of tanning, the exterior of the hides may be so hardened that 
penetration by the liquor into the interior becomes impossible. 
Smooth grain and fibers completely tanned are obtained only 
when the rate of increase of tannin strength is very low. 

Sole leather is sold by weight, and as the cost of the hide 
is from 50 to 70 per cent of the cost of the finished leather, 
the tanner's main object is to produce as many pounds of 
leather as possible from a given weight of hide. Whatever 
degree of success he may have is spoken of as a "gain." 
Thus, for 100 lb. of green-salted hides the tanner can obtain 
from 60 to 80 lb. of leather, so he has a gain of from 60 
to 80 per cent; but from 100 lb. of dry hides he will make 
from 150 to 185 lb. of leather, and so has a gain, of from 
150 to 185 per cent. 

For the manufacture of sole leather, either green-salted, 
dry-salted, or flint hides may be used. In the preparatory 
treatment they are soaked, washed, unhaired, and fleshed as 
already described. They are then placed over sticks and sus- 
pended in cold water over night. It is not customary to bate 
hides for this class of leather. 

Three general methods are used in the manufacture of sole 
leather, namely, oak, hemlock, and a combination of both, 
known as union. True oak-bark tannage is practically a thing 
of the past, and what is sold as oak is in reality chestnut oak. 
Hemlock leather is produced by the methods acid and non- 
acid. 

Oak leather. — Leather made from hides that have been 
tanned with oak bark is distinguished by its light color and 
firm texture. This tanning material imparts a bloom to the 
leather which may or may not be removed, according to the 



266 PRACTICAL TANNING 

demands of the trade; if it is removed, the leather is spoken 
of as "scoured." 

On removal from the cold pool, the hides are ready for 
the actual tanning process. They may be carried through as 
whole hides, but they are generally cut into sides before enter- 
ing the rocker. The rocker system consists of a series of 
vats 8 ft. long, 6 ft. wide, and 5-J ft. deep arranged so that 
the liquor from the bottom of one pit overflows into the top 
of the next. The liquor is supplied to the head or strongest 
liquor vat containing the most tanned hide, and gradually 
works its way through all of the vats in succession, being 
weakened or sapped in each by the presence of the hides. It 
finally reaches the tail rocker-vat where it meets the fresh 
hides, and then flows to waste or is pumped over the leaches. 
The stock suspended on the frame of the rocker is moved 
slowly up and down, which serves the double purpose of agi- 
tating the liquor and producing an even color on the grain. 
This rocking also hastens the tannage, and by preventing the 
hides from touching removes the danger from untanned places 
known as "kiss spots." 

The rocker liquor, being acid in character, serves to neu- 
tralize the lime present in the stock, and at the same time 
produces a swelling or plumping effect on the hides. Much 
care is necessary during this operation, as the quality of the 
leather is determined by the attention given to the hides while 
they are in the rockers. 

The liquor used in the rockers should contain sufficient acid 
to perform its function as mentioned, and in the tail liquor 
is usually about 0.6 per cent. This acid is produced naturally 
by fermentation of the glucosides, or may be obtained by add- 
ing lactic acid. The strength of the tail rocker liquor should 
be about 10°, and 18° in the head rocker. 

The time that the hides remain in the rockers varies ac- 
cording to local conditions, but 15 days is about the proper 
period. The hides are in a plump condition on removal from 
the rockers, and the grain is sufficiently tanned to withstand 
the astringent action of the stronger liquors. 



VEGETABLE-TANNED SOLE LEATHERS 267 

After the rockers, the hides are treated in the layers. These 
layaway vats are usually somewhat larger than the rockers, 
and as a rule the hides from three rockers can be accommo- 
dated in one layer. In these layers the hides are laid out flat, 
one at a time, and sprinkled over with coarsely ground bark. 
When the hides are set, a concentrated solution of the tanning 
material is pumped in until the pit is full, and the hides are 
allowed to remain undisturbed for a definite period, as given 
below. 

Some tanners prefer to substitute the first layer pit by a 
press layer system. In this case the hides are thrown into 
the pit, but no ground bark is used. Strong liquor is added 
to the head press-layer pit, and gradually, by overflowing 
from one pit to the next, presses the weaker liquor towards the 
tail-press layer. The time of treatment in the press layer 
is usually about 8 days and the strength of the liquor runs 
from 20 to 28° barkometer. 

Where still layers are employed, the time in the first layer 
is usually about the same as for a press layer, or about 8 
days. Whether the layer be still or a press layer, the sappage 
is fairly high, owing to the fact that the stock is in a very 
receptive condition at this stage. 

From the press layer or first layer the hides are transferred 
to other layers, the number and strength of which depend 
largely upon the idea of the individual tanner, but commonly 
three or four. These layers are sometimes spoken of as "hand- 
lers" or "dusters." 

The following schedule represents typical practice in an 
oak-bark tannery : 

Strength of liquor 
Treatment Tunc, days degrees barkometer 

Rockers 15 10 to 18 

First or press layer 8 20 to 28 

Second layer 12 34 to 38 

Third layer 16 36 to 38 

Fourth layer 25 40 

Fifth layer 32 SO 

In the above description of an oak-bark tannage it is as- 
sumed that the agent is true oak bark. 



268 



PRACTICAL TANNING 



When the tannage is complete, the sides are taken from the 
last layer and thrown into warm water to clean the grain 
from sediment. After rinsing, they are piled up to drain. 
They are then swabbed with cod oil or a mixture of this and 
mineral oil, and hung on sticks in the drying loft. This 
loft is so arranged that the window may be closed and dark- 
ened at the start, and heat and a good circulation of air pro- 
vided later. This is an important factor in the proper dry- 




Figure 69. — Sole leather rolling-jack. 

ing of sole leather, as drying too quickly causes a cracky 
grain, while drying too slowly results in mold. 

When thoroughly dry, the sides are removed from the loft, 
brushed with water, and placed in piles to sammie. The 
properly tempered sides are oiled on the grain and rolled. 
They are then returned to the loft, and when dry are ready 
for market. The rolling is accomplished on a machine con- 
sisting of a heavy beam on the side of which is a brass wheel 
(figure 69). This wheel 'is about 8 inches in diameter and has 
a 6-inch face. The leather is held under the roller on a brass 
bed conforming to the arc described by the roller. A foot 
lever raises the bed and thus produces the necessary pressure. 



VEGETABLE-TANNED SOLE LEATHERS 269 

Rolling serves to smooth the grain and compress the leather 
at the same time imparting a desired polish. Owing to a 
demand for a full cutting leather, the above procedure is 
often modified. This is especially true in the case of extract- 
ing and loading leather, the process for which will be given 
in detail under the head of union tannage. 

Non-acid hemlock tanning.— As a rule, dry hides are 
used in the manufacture of non-acid hemlock leather. After 
soaking, depilating, de-hairing, and fleshing, the hides, which 
have been cut into sides, are run in the paddle for a few 
hours with an acid color liquor consisting of spent liquor from 
the tail handler of about 8° bk., and containing about 0.6 
per cent of lactic acid. They are then toggled together and 
placed in the tail handler pit. The handler pits are arranged 
in series like the rockers described, that is, the strong liquor 
enters the head pit and is then pressed toward the tail by flow- 
ing from the top of one pit to the bottom of the next. During 
the flow of liquor through the series there is a sappage of 
about 6° bk., the liquor entering the head handler from 14 
to 18°, and leaving the tail handler at about 8°. By means of 
a power-driven reel the sides are changed several times each 
day for the first three days, being pulled and replaced in 
the pits. This changing exposes more surface to the action 
of the tan, at the same time stirring up the liquor. After 
the third day, and each day thereafter, the hides are reeled 
forward into the stronger liquor until the head handler is 
reached. The time in this handler is from 12 to 15 days, 
during which time the stock has become plumped and the 
grain well set. On removal of the sides from the head han- 
dler they are untoggled and placed in the first lavaway. The 
strength of the first layer is about 20° bk., and is usually an 
old liquor that has been sapped in another layer. The hides 
remain in the first layer for 7 days. They are then pulled and 
transferred to the second layer, where thev remain for 11 days 
starting with a 22° liquor. This solution is also a sapped liquor 
from a stronger layer. The third layer liquor stands at 23° 
and in it the stock remains for 12 days. This solution is usu- 



270 PRACTICAL TANNING 

ally made fresh from leach-house liquor strengthened with ex- 
tract. In the fourth liquor the hides are allowed to remain 
for 20 days, the strength being 25°. The fifth layer should 
have a reading of 28°, and the stock should remain in it for 
21 days. The sixth-layer liquor should stand at 30° and the 
time should be 28 days. In the fourth, fifth, and sixth layers 
the solutions are made from sweet liquors from the leach- 
house, which have been strengthened with extract. The 
sapped liquors from the first, second, and third layers 
are used as handler liquors, while these layers are made 
up from sapped liquors from the fourth, fifth and sixth 
layers. 

The reason for this particular method in handling the yard 
liquors is based upon the fact that the hides require a cer- 
tain amount of free acid to produce the necessary plumping 
in the early stages of tanning. This acid is produced by fer- 
mentation of the liquors. By the time the stock reaches the 
fourth layer the plumping is complete, and so the hides should 
then only be treated with acid-free liquor. The reason for 
increasing the strength of the liquor is due to the fact that, 
after the tanning content of the hide equals that of the liquor, 
no more tanning will take place. In other words, the strength 
of the liquor should always be greater than the tannin con- 
tent of the hide. The stock, on coming from the last layer, 
is thrown into a pool of warm water to remove the sediment 
from the surface of the leather, or it may be washed in a 
drum. From this point on the leather may be finished as 
will be described under union tannage. 

Acid hemlock leather. — By this is meant a variety of hem- 
lock sole-leather which has received its plumpness by means 
of sulphuric acid. The bulk of acid-hemlock leather is made 
from dry hides which have been de-haired by the sweating 
process. The hides, as they come from the beam-house, are 
placed in color vats, where they come in contact with spent 
liquor, which gives them a surficial tannage on the grain and 
sets the color. After this treatment they are suspended in 
a 0.1 to 0.3 per cent solution of sulphuric acid where they 



VEGETABLE-TANNED SOLE LEATHERS 271 

remain until the desired plumpness is secured, and are then 
ready for the tanning liquor. 

The hides go direct to the first layer liquor,, and on account 
of the abnormal plumping it is not necessary to start with 
weak solution as is the case with other tannages. There 
are, therefore, no rockers or handlers in the acid-hemlock 
process, but strong liquors are employed from the start. The 
stock enters the first layer which is 38° bk., and remains in 
this liquor for 8 days. During this time the liquor is sapped 
to about 20°. The density, however, is no indication of 
strength of the liquor, for the reason that the hides carry in 
sulphuric acid and sulphates which materially raise the gravity. 
The spent liquor, therefore, is run to waste as its sulphuric 
acid content retards the absorption of tannin. Some tan- 
ners have made the mistake of returning the spent liquor to 
the leaches. When this is done, the whole yard eventually 
becomes saturated with sulphuric acid, and no tannin can be 
taken up by the hides. From the first layer, the sides are 
transferred to a second layer, where they remain for 11 days. 
The second layer liquor has a strength of 40° bk. The 
sapped liquor from the second layer becomes the strong liquor 
of the first layer. If low in barkometer, the spent second 
layer liquor is sometimes built up with strong liquor from the 
last layer. 

In an acid-hemlock yard the leach-house liquor is usually 
built up to strength with extract, either hemlock or chestnut 
extract being used. Any excess of liquor from the second 
layer, as well as the sapped liquor from other layers, is re- 
turned to the leaches, and made up to strength by further 
leaching and by the addition of extract. 

From the second layer, the stock is transferred to the third 
layer, where it remains for 15 days with a density of 42° 
bk. at the start. In the fourth layer the hides remain for 24 
days, the strength of the liquor also 42°. Treatment in the 
fifth layer is for a period of 24 days, the initial gravity being 
44°. The sixth layer has a gravity of 48°, and in it the hides 
remain for 27 days. 



272 



PRACTICAL TANNING 



From the sixth layer the hides are thrown into a warm pool 
to remove the excess of liquor and clear the grain. They 
are then extracted and finished as desired. 

Union leather. — A combination of hemlock with chestnut 
oak extract gives a satisfactory leather, and one having a color 
closely resembling oak-tanned stock. The combinations used 




Figure 70. — Mechanical transfer in the tan-yard, showing pack going 

to rocker. 



are as numerous as there are tanneries producing this grade 
of leather. In some plants the tanner depends upon his leaches 
for making the combination liquor, while others depend en- 
tirely upon extracts for this purpose. Although, strictly speak- 
ing, a union tannage is supposed to be a mixture of hemlock 
and chestnut, it will be found that many tanners add other 
extracts such as quebracho, mangrove and myrabolans. Most 
of the union leather is cropped ; that is, the bellies and shanks 
are cut from the sides, leaving what is known to the trade as 
a "bend." These bends bring a higher price than the same 



VEGETABLE-TANNED SOLE LEATHERS 



273 



leather sold in sides, because they can be cut to better advan- 
tage in making soles. The bellies are used for inner-soling, 
where less wearing quality is required. 

Green-salted hides are generally used for making union 
leather. They are soaked, limed, de-haired, fleshed, fine- 
haired, and placed on sticks in the cold pool over night, when 




Figure 71. — Mechanical hoist for moving hides. 

they are ready for the rockers. The rocker-pits (figure 70) 
are arranged in series, usually in two rows, connected in such a 
manner that the liquor in them may be pressed forward, up 
one side and down the other; in other words, a sort of an 
exaggerated circle. Fresh stock from the beam-house is put 
into the tail pit, which contains no liquor. Fresh liquor from 
the extract-house or leach-house is pumped into the head pit, 
which contains the hides that have been in the rockers the 
longest time. As the strong liquor enters the head pit, the 
liquor in it overflows to the bottom of the next pit, which in 
turn overflows to the next, and so on until the tail pit is full. 



274 



PRACTICAL TANNING 



To secure an empty pit for the next pack, the hides in the 
most advanced pit are transferred (figure 71) to the layer, 
and the liquor in that vat is pumped to the next in the series. 
The overflow causes a change of liquor throughout the series. 
The liquor in the tail pit may flow to waste, or it may be 
pumped back to the extract or leach-house. The common prac- 




Figure 72. — View in the tan-yard, showing series of layers. 

tice is to pump back twice to leach-house and once to waste. 

The frames on which the hides are suspended rock slowly 
up and down, thus preventing the setting of insolubles, assist- 
ing in the production of uniform color and penetration, and 
obviating what are known as kiss spots. 

The greatest care should be exercised in the rockers, as it 
is here that the character of the leather is formed. Attention 
must be given to the strength of the liquor, and the amount 
of free acid and tannin carefully checked. Under no circum- 
stances should the rocker liquors be mixed with those from 
the other parts of the yard. Barkometer readings may be 



VEGETABLE-TANNED SOLE LEATHERS 275 

taken to assist in regulating the liquor, but they are not a 
safe guide without occasional laboratory checks. 

Assuming a rocker system in which the hides remain for 
15 days, in the tail-pit there should be from 0.5 to 1 per 
cent of tannic acid and from 0.25 to 0.33 per cent of free 
acid, estimated as acetic. These should increase gradually un- 




Figure 73.— Cropping. 

til in the head rocker there should be 2\ per cent of tannic 
acid and 0.6 to 0.7 per cent of free acid, estimated as acetic. 

Assuming again that the union leather is being made with 
an extract tannage, the proportion should be as follows : 

Tannage extract Per cent 

Chestnut wood !•? 

Chestnut bark • 45 

Hemlock bark 40 

On removal from the rockers, the hides next enter the press 
layers. These consist of a series of vats arranged in some- 
what the same manner as the rockers, and the liquor is pressed 



276 



PRACTICAL TANNING 



forward in the same way, working from head to tail pit. 
The hides are taken from the rocker frame and thrown into 
the empty tan pit one at a time. Over each hide is dusted some 
chestnut-oak bark, before the next hide is placed in position. 
This powdered bark tends to keep the hides separated, and 
so allows more uniform contact with the liquor. 




Figure 74.— Cropped hides and bellies ready for final layer. 

Numerous methods are employed for handling the stock 
in the press layers. A common method is to have two rows 
of five vats, the number of the series depending upon the 
size of the tannery and the quantity of stock being treated. 
One pack enters and one is removed from this set of layers 
every other day, thus making 20 days required to work the 
hides through the press layers. The liquor in the head press 
layer should stand at about 40° bk., and should contain 4 
per cent of tannic acid and about 0.6 per cent of free acid as 
acetic. During the passage through the press layer the liquor 
should be sapped so that in the tail press layer there should 



277 



VEGETABLE-TANNED SOLE LEATHERS 

be about 2\ per cent of tannin. A good combination for the 
press layer is as follows : 



Per cent 
20 



Tanning extract 

Chestnut wood 45 

Chestnut bark 35 

Hemlock bark 

The hides for the press layer are next transferred to the first 

layer liquor. The layer-pits (figure 72) are not connected 




Figure 75.— Quirin press or wringer. 

with overflow as is the case with the rocker and press layers, 

and the liquor in them is not changed during the 7 days that 

the hides remain in them. No bark is used for dusting m the 

first layer, and the strength of the liquor should stand at 42° 

bk. The tannin content of the first layer should be about 4* 

per cent, and should be made up as follows : 

_ , . Per cent 

Tanning extract 

Chestnut wood ^ 

Chestnut bark 35 

Hemlock bark 

The temperature of the first layer liquor should be 95° F. 
The second layer liquor is made up of the same materials 



278 PRACTICAL TANNING 

and proportions as the first layer, except that the density is 
raised to 46° bk. and the tanning content therefore increased 
to 5 per cent. The hides remain in the second layer for 12 
days, during which time they are not removed or the liquor 
changed. On removal from the second layer the hides are 
cropped (figure 73). The cropped backs are placed in the 




Figure 76. — Extract wheels. 

third layer pits and the bellies thrown in on top (figure 74). 
The liquor in the third layer is made up entirely of quebracho 
extract at a density of 55° bk. and at a temperature of about 
115° F. No bark is used to dust the backs, and they remain 
in this liquor without changing for 35 days. 

Extracting. — As the hides come from the third layer they 
are thrown into water at 100° Fr for an hour, and then passed 
through the wringer (figure 75). The well pressed and fairly 
dry backs are next placed in the drum (figure 76), about 100 
backs constituting a pack, and while the drum is in motion 
500 lb. of 100° bk. quebracho extract at a temperature of 



VEGETABLE-TANNED SOLE LEATHERS 



279 



150° F. is pumped in. The drum is run for 1^ hours, by 
which time practically all of the extract has been absorbed. 
From the extract wheel the backs go to the tempering pit, 
which contains a quebracho extract of 45° bk. and at a tem- 
perature of 80° F., where they remain 4 days. 

Bleaching. — On removal from the tempering pit, the backs 




Figure 77. — Ready for the bleach. 

are suspended on sticks (figure 77), and hung for 7 minutes 
in fresh water at a temperature of 125° F. The frame is 
now lifted, and the hides immersed for 7 minutes in a weak 
alkali solution (figure 78), the strength being 0.3 per cent 
of sodium carbonate on the weight of the water, and the tem- 
perature 125° F. From the alkali the backs pass to the first 
acid dip, in which 1.5 per cent of sulphuric acid on the weight 
of the water is used. The time and temperature are the 
same as for the other treatments. The backs now go to a 
second acid solution which, however, is somewhat more di- 
lute. To remove the excess of acid the leather is clipped in 



280 PRACTICAL TANNING " 

plain running water for 7 minutes. After bleaching, the 
hides are passed through the wringer, and are ready for load- 
ing. Figure 79 shows a cross section of a standard bleaching 
machine. 

The bellies from the third layer are not extracted, but after 
washing in warm water are bleached in the same manner as 




Figure 78, — Hides suspended in the bleach. 

described for backs. They then receive the same finishing 
treatment as the backs. 

The hides, as they come from the wringer, are placed in a 
drum (figures 80 and 81) and about 50 lb. of crystal magne- 
sium sulphate is added for each 100 hides. The door is then 
closed, the mill started, and a mixture of 175 lb. of glucose, 
6 gallons of sole-leather oil, and 1 gallon of cod oil, at a tem- 
perature of 150° F., is added through the trunnion. The 
stock is run for a half -hour. The hides are then set out on 
a Quirin press and go to the loft. The dyeing of sole leather 
must be carried out with great care, otherwise a dark and brit- 



VEGETABLE-TANNED SOLE LEATHERS 281 

tie grain is likely to result. The usual procedure is to hang 
the leather over sticks, and for the first two days keep the 
loft dark and as cool as possible, but with proper ventilation. 
The temperature of the loft is then gradually raised and light 
admitted. The time required for dyeing varies with the cli- 
mate, season of the year, and conditions of the loft. 




Figure 79. — Bleaching machine. 

When the leather is thoroughly dry it is taken down and 
dipped in warm water containing a small quantity of glucose 
and then piled down to sammie, which takes from one to two 
days. When properly tempered, the grain is wet uniformly 
with warm water, and given a coat of cod oil. While still 
in this damp and oily condition the leather is set out and 
rolled for the first time (figure 83). The rolled stock is again 
taken to the dry loft (figure 84), and this time suspended by 
one end (figure 82), and when dry is again rolled. Some 
tanners apply a seasoning after the first rolling, which adds 
to the appearance of the leather on re-rolling. In place of 
the second rolling the leather is sometimes seasoned (figure 
85) and brushed on the machine shown in figure 86. After 
the second rolling or brushing the leather is ready for sorting 
and grading for market. 

Rapid sole leather tannage. — On account of the immense 
sum of money represented in hides tied up in the process of 
making sole leather, many rapid tannages have been pro- 
posed, some of which are of proved merit, while others are 



282 



PRACTICAL TANNING 



entirely valueless. Practically all of the rapid tannages depend 
on constant agitation of the hide in the presence of the tanning 
agent. It is in the method of securing this agitation that the 
various systems differ. Most of the quick tannage processes, 
however, are still in the experimental stage, but whether they 
will be able to compete with the old-style methods remains 
to be seen. 

One of these rapid tanning processes depends for its effi- 




Figure 80. — Placing in loading wheel. 

ciency upon rockers arranged as described under the regular 
sole leather process. The hides, on coming from the beam- 
house, are suspended in frames and treated just as given under 
union tannage. On removal from the rockers they are at 
once put in the drum, and wheeled with strong extract for 
a period of from one to several days. They are then bleached 
and finished in the usual manner. 

Some processes depend upon tawing with alum and salt to 
set the grain before entering the strong liquor. 



VEGETABLE-TANNED SOLE LEATHERS 283 

Many processes have been patented in which the use of a 
revolving drum is the principal feature. The size, shape, and 
arrangement of the hides in the drum are all features which 
have been patented. Some drums are provided with frames 
to which the hides are attached, thus causing the liquor to fall 
over the stock. In other processes the hides are fastened to 
hooks in the drum. In all of the methods the grain is first set 
with dilute liquor, and then the concentrated extract is applied. 




Figure 81. — Removing from loading wheel. 

The chief objection to rapid tanning is the low gain, al- 
though this may be counteracted by loading. The following 
complete description of one of the rapid tanning processes may 
be of interest: 

Tanning zvith chestnut extract.- — This extract, prepared with 
care, is practically a pure solution of chestnut wood tannin, 
rich in tanning power per unit of density, and soluble to a 
high degree. It will form liquors free from sediment or 
liquor-filth, well balanced in tannin and non-tannin for oak 



284 



PRACTICAL TANNING 



and hemlock yards, and suitable for tanning hide fiber quickly 
and thoroughly. 

For color reasons, chestnut extract should be well incorpo- 
rated with the leach liquors. Its natural color is brown, but it 
becomes red by treatment. Mix as much as 75 per cent with 
the leach liquors, and the bark color will dominate. Tan the 




Figure 82. — Setting-out after tempering. 

stock in chestnut alone and the color will be "on the brown.". 
This is the only color secret in the use of chestnut extract. 
Put the extract on the head leach, through the sprinklers, or 
a little at a time as the leach fills with bark, and take down 
the liquors in the customary manner, making the draw of the 
desired barkometer average. As the yard becomes saturated 
with the cnestnut, several things will be observed — the packs 
will feed more rapidly, they will "stand up" higher, and the 
plumpness put into the stock in the sours will hold up to 
the rolling room. This is because the liquors sent to the stock 
are richer in tannin per unit of barkometer, without an in- 



VEGETABLE-TANNED SOLE LEATHERS 



285 



crease of the liquor-filth which impedes entrance of the tannin 
into the fiber of the stock. Leather is made in the beam- 
house and the sour end of the yard; almost anything can be 
done to it if proper beam-treatment and plumpness are parts 
of its record. After the handler period is past, the stock 
should enter the heavier liquors in a condition of plumpness 




Figure 83. — Rolling-jacks. 

and grain desired in the finished product, and from that point 
forward it should be struck steadily and persistently, with such 
frequent shifting as will keep the feeding process continuous. 
The function of chestnut extract is thus made clear: It is 
simply a tanning agent with souring properties midway be- 
tween hemlock and oak, aiding the handlers in one and re- 
straining them in the other. No other extract possesses this 
unique property. The amount of combined tannin that can 
be put into a hide depends almost wholly upon the degree in 
which the initial plumpness is retained during the passage of. 
the stock through the true tanning liquors, those beyond the 



286 



PRACTICAL TANNING 



handlers. If these liquors are clean and grade up from 20° 
bk. in the first layer to from 50 to 60° in the last, the com- 
bining process will proceed uniformly and steadily, flanks 
will be full and firm, the cut will show as much color from the 
one side as the other, and the "white streak" will be firm and 
plump. Such leather has good market qualities, and also has 




Figure 84. — Drying-loft. 

more room for finishing material and a larger area of hide- 
fiber to take the tannin. Chestnut extract promotes exactly 
these conditions, with, at the same time, a beneficial effect on 
the sour end of the yard. 

There are various ways of using this extract: Some tan- 
ners put it directly on the leaches, and there allow it to dissolve 
and percolate through the ground bark. The chief advan- 
tage claimed for this is that the disagreeable bluish-gray color 
on the stock is avoided. Other tanners dissolve the extract 
in a separate tank and then run it on the leaches through the 
sprinklers. Others prefer to dissolve the extract separately, 



VEGETABLE-TANNED SOLE LEATHERS 



287 



then mix the solution with bark liquors as they come from 
the leach-house. These methods, however, are not the latest 
nor the most approved, practical experiments having shown 
that chestnut extract is used most successfully along other 
lines, which may be described as follows : 

The hides are soaked, fleshed, limed, and de-haired in the 



! KNHtti 



tmf?^ 




Figure 85. — Applying the bright finish to sole leather. 



usual way. After de-hairing, they are well worked on the 
grain, then left hanging over night in the cold water pool, to 
which lactic acid has been added. For ordinary packs, 40 
lb. will be sufficient. As they are plumped, and the fixed 
lime is also neutralized, the ordinary time in the handlers 
may safely be considerably reduced. Coming from the cold 
water pool, the hides should again be washed on the grain be- 
fore going to the liquors. The green pack is given a week in 
the handlers, which are soured to the proper degree by addi- 
tion of lactic acid. The hides go from the handlers through 
the first two layers until struck, after which they are run 



288 PRACTICAL TANNING 

through a roller press, and are then ready for the drumming 
process. 

The extract is poured into hot water, and the solution is 
run on the stock through the gudgeon at about 16° bk. The 
drum is revolved slowly at first. The two essentials at this 
stage of the process are the maintenance of the liquor strength 




Figure 86. — Brushing machine for sole leather. 

and keeping the stock comparatively cool. When the hides 
become warm, they should be withdrawn and allowed to cool. 
During this interval the old drum liquors are run to the 
handlers and new liquor is supplied to the drums. 

After the leather is thoroughly tanned, weight is given by 
putting it in a drum together with a certain amount of undis- 
solved extract, and then drumming long enough to have it 
absorb the extract. It is then finished as usual. One of the 
advantages of the drum system is that entirely sweet liquors 
can thus be given to the stock, since the natural resistance of 
the fiber to the penetrating power of the tannin is overcome 
by the agitation. However, it can readily be seen that the 
old drum liquors sent to the handlers will not contain a 
sufficient amount of free acids — other than tannin — requisite 
for the holding of the plumpness of the hides; hence it is 
necessary to add lactic acid to the handlers so that the proper 
relations of the acids may be maintained. As there is an 
absence of natural lactic acid, the best results are obtained 



VEGETABLE-TANNED SOLE LEATHERS 289 

by adding the commercial article to the head handler liquor 
in the proportion of 1 lb. of lactic acid to every 100 lb. of 
hides, green weight. Besides adding to the head-handler 
liquor, it is advisable to add lactic acid to the other handlers 
half way down the series, in quantities growing smaller from 
the head liquor. 

Chestnut extract is a valuable tanning material for manu- 
facturers of heavy leather, its tannin being so easily available 
it is one of the most acceptable on the market. Light skins, 
prepared as for any other tannage, may be tanned by sus- 
pension in chestnut liquor or drummed in liquor made direct 
from the extract, or from a mixture of two extracts. Skins 
intended to be colored subsequent to tanning are usually tanned 
direct in the extract liquor, with occasionally a re-tan in sumac. 
Stock to be run in the natural color is usually struck in the 
mixture, giving the shade desired. With very thin leathers, 
the main requirement of the tanning material is that it shall 
be clean, bright, and quick in action. 

Light hides for side leathers are first put through a series 
of sour liquors, in which they are plumped. The liquors 
are prepared by direct solution of the extract in water or 
freshly made bark liquor; thus prepared, they are given sweet 
to the nearly struck goods, usually as layaways, not infre- 
quently in revolving drums. These stocks are always tanned 
out in relatively weak liquors, rarely exceeding 15° bk., as 
freshly prepared. Tanning is then completed in drums. 
Where a particular color quality is desired, the leather is re- 
tanned with suitable material, such as gambier, mimosa, que- 
bracho, sumac, etc., according to the shade or color condition 
desired. 

Drum tanning for sole and belting leathers. — In using 
quebracho, 85 per cent, and oak, 15 per cent, a flrst'-class piece 
of leather can be made, by carrying out the following process : 
After putting the hides through the beam-house, a 4° liquor 
is made of quebracho and oak extract as mentioned above. 
In preparing these liquors, make up 3,000 gallons of 4° solu- 
tion in the cooler, then add 4 gallons of acetic acid and 1 gal- 



290 PRACTICAL TANNING 

Ion of dermi forma. After standing 5 or 6 days, run the 
liquor on to the green hides. Strengthen each day with enough 
liquor to fill each rocker for green hides in turn. Raise the 
liquor 3° daily until the strength is 20° bk. Add each day 1 
gallon of dermiforma and 6 quarts of acetic acid, then feed 
from head rocker, keeping liquors at 20 to 22°. Never have 
the tail liquor above 4°, as quebracho extract penetrates much 
faster than oak extract. It is safe if the tail falls to 3°, but 
it is best to keep it at 4°. There should be 10 rockers in a 
section, and the hides should hang 20 days. Then take them, 
from the rockers and crop them for the drums. 

Put 50 backs in a drum, fill the drum two-thirds with 75° 
liquor, and run for 48 hours without changing the liquor, 
but watch the temperature and keep it below 105° F. After 
the 48 hours, discharge all of the liquor and fill again with 
75° liquor, filling the drum only half full this time. The 
drum should be large enough to hold 25 barrels when half full. 
Drum 24 hours, when the hides will be tanned throughout, 
plump and of fine color. 

The hides must be well toggled together — grain inside — to 
prevent the grain being damaged by rubbing together. After 
a 72-hour run, take the leather from the drum, and lay it 
away in a 75°, liquor for 4 days. Put 300 backs into a vat 
8 by 9 by 6 feet, with 50 lb. of sumac to 100 backs. On the 
fourth day, raise the stock, run it through a wringer, and put 
it back into the drum. Add 3^ lb. of quebracho extract to 
each back, dissolved and not diluted. Put 50 backs into the 
drum with 175 lb. of extract, and drum for 30 minutes. Then 
take them from the drum and throw into a sour liquor. It 
will be found that by running the backs through the wringer 
or press the extract will penetrate much better, and little will 
remain on the surface. The sour liquor should be 25 to 30° 
bk. After lying in the sour liquor for 24 hours the leather 
is ready for bleaching. It is advisable to scour lightly on 
the grain. Have one pit holding 750 gallons of water, two 
of the same size for soda, and two for acid. Put 22 lb. of 
soda ash in the first pit and 3 lb. in the second ; also 30 lb. of 



VEGETABLE-TANNED SOLE LEATHERS 291 

sulphuric acid in each, and heat to 125° F. Hang 8 backs in 
each pit; strengthen after every 40 backs, putting 4 b. of soda 
into the first pit, but none in the second, as puling stock 
from the first to the second will maintain the soda content 
in the second pit. Also add 4 lb, of sulphuric acid into each 
pit for 40 backs. From the pits the backs are put into clear 
water for 2 hours; then oiled, and run through the press or 
hung up to drain; preferably the latter, as the press draws 
more or less extract to the surface. For oiling use | lb. of 
cod-liver oil, or a mixture of this and a mineral oil Re- 
garding sugar and glucose, putting them in with the oil and 
then drumming is the cheaper method, but best results are 
obtained by re-tanning. 

When dry, dip the leather into water for rolling. It prop- 
erly looked after in the rolling room, the backs will look just 
like vat-tanned oak backs, only they will be firmer and of a 
brighter color. From 70 to 75 per cent finished gam can be 
made by this process. 



CHAPTER X 

BELTING LEATHER 

The description of belting leather in this chapter is taken 
largely from a lecture given by F. H. Small before the tanning 
and applied leather chemistry students of Pratt Institute, Brook- 
lyn, N. Y., for which the author desires to give him credit, 

Necessary characteristics. — Leather to be used in the man- 
ufacture of belting should have the following characteristics : 

Good driving surface, with sufficient friction between belt 
and pulley to keep slippage small and enable the belt to carry 
its load when slack, whereby useless waste of power at the 
bearings is avoided. 

Lateral stiffness coupled with pliability: Stiffness to pre- 
vent the belt from curling at the edges when shifted, and 
from twisting and waving; and pliability to enable the belt 
to hug the pulley, wrapping itself around to secure the larg- 
est possible arc of contact, and enable it to alter its shape 
with the minimum of internal resistance as it travels round 
the pulley. 

High tensile strength, so that it may carry a heavy load 
without breaking. 

Little stretch but considerable elasticity: Little stretch so 
that it will need to be shortened as seldom as possible, doing 
its work uninterruptedly ; and elasticity that it may easily take 
up and let go its load as it travels round the pulley. 

Straightness, so that it may run true on the pulleys. 

Resistance to external conditions, (such as heat, moisture, 
chemicals, etc. ) so that it may do its work in any place at any 
time enduringly. 

Low initial cost. 

It is generally admitted that leather comes nearer to pre- 
serving all of these qualities than any other material. Many 
of the qualities specified, however, are almost opposite, and it 

292 



BELTING LEATHER 293 

is apparent at the outset that no material and no leather can 
meet all of the requirements with full satisfaction. Lateral 
stiffness is not compatible with pliability ; elasticity rarely goes 
hand in hand with no stretch. The best we can hope to do, 
therefore, is to make a leather that will have the desired qual- 
ities in the largest degree, and in which we have compromised 
some of the incompatibles. 

Leathers used in belting. — There are various kinds of 
leather used for making belting, but the most popular belting 
is that called "oak-tanned leather," the general conception of 
which is belting made from leather tanned with oak bark in 
the old way. While it might not be safe to say that after 
diligent search it would be impossible to find a small amount 
of leather that has been tanned in this way, the quantity 
would be a very small proportion of the whole. The terms 
oak, hemlock, and union have gradually grown to have less 
and less significance when applied to leather. This is not 
saying that there are no manufacturers using large quantities 
of oak bark in making their oak-tanned leather, but it is 
indicative of the general trend. 

Bearing in mind that the term "oak-tanned" as used today 
stands in general for a "type of leather" rather than for a 
"true. oak-bark tanned leather," the description of the manufac- 
ture of oak-tanned leather for making belting may then be 
understood. 

It will perhaps be as well to mention the fact that by no 
means is all of a hide usable for making leather belting; in 
fact, ordinarily only about a third of the hide is so used, the 
part used being called a belting bend. For a cheap grade of 
belting, other parts of the hide, particularly the best part of 
the shoulder, are sometimes utilized. 

Razv material. — The belt-maker, who is also a tanner, tans 
the whole hide, and his raw material is the green hide. The 
raw material of the belt-maker who is not a tanner is a 
market or belting butt, as belt bends are not commonly on 
. the market. A belting butt is that part of the hide left after 
cutting off the bellies, head, neck, and tail. The bellies are 



294 PRACTICAL TANNING 

cut off at the flank on a line parallel to the backbone; the 
head and neck in a line at right angles to the backbone. 
This butt is divided by the belt manufacturer into a belting 
bend and a trimmed shoulder by cutting the butt at right an- 
gles to the backbone at a point 54 inches from the tail. The 
bellies, heads, and shoulder are collectively called the offal. 
The butt and offal are sometimes processed independently in 
the tannery, but the hide is at least started as a whole, and so 
we may begin our consideration of the leather manufacturing 
process by devoting a few moments to one of the raw mate- 
rials — the hide. 

Hides used for tanning into belting leather are commonly 
green-salted packer hides. They should be free from brands, 
and as far as possible free from flesh cuts caused by poor 
flaying, from scratches on the grain whether or not healed, 
and from grub-holes — whether or not healed. These all will 
constitute defects in the finished leather, and shorten the life 
of the belting made therefrom. 

The take-off of American hides is reasonably good, more 
fault having to be found in this connection with foreign hides. 
Fortunately the scoring is usually worst on the belly and 
shoulder-parts of the hide, which are not used for belting; 
but the cuts in this case lessen the value of the offal. 

Barbed. wire is perhaps not as common now as some years 
ago, but at that, it is difficult to secure hides free from the 
scars, long and short scratches, each of which may possibly 
be the nucleus of a crack which is at first surficial, but will 
ultimately work into, the leather deep enough to cause the 
belt made from it to give way. 

It requires no argument to demonstrate the damage done 
to a hide by the larvae of the warble fly. These work their 
way out through the skin, leaving behind a hole, which, even 
though it may heal over, will always be a weak and unsightly 
spot in the finished leather. It is not an uncommon sight to 
see skins so full of grub-holes that they look as though they 
had been riddled by a shot-gun. Within recent years, how- 
ever, the U. S. Department of Agriculture, co-operating with 



BELTING LEATHER 295 

the Tanners' Council, has done much to eliminate this source 
of damage. 

Manufacturing processes. — For belting leather, the best 
hides will be none too good, so the first step in the process of 
leather making will be to secure the best hides possible. 
These hides will then need preparation for tanning, and are 
put through the regular beam-house processes of soaking, 
fleshing, liming, de-hairing, beaming, and de-liming. The 
old-time tanner who said that the quality of his leather was 
made in the beam-house, knew whereof he spoke, and the 
beam-house work will merit and demand the most careful 
attention. 

The points of most importance in the beam-house practice 
when belting leather is to be made are as follows : 

1. Good hides, sound, green-salted, unbranded, well flayed, 
and so far as possible free from grain scratches and grubs. 

2. Thorough soaking. 

3. Average liming, as for instance a 3 to 6-day liming in 
limes of progressive sharpness and newness, the limes con- 
taining 4 to 5 lb. of lime and not over 1 lb. of sodium sulphide 
per 100 lb. of hide. 

4. Drenching or bating the hides to remove surface lime 
and bring down the grain. 

In the United States the common practice is to carry the 
hide through the beam-house as a whole hide, and usually 
also through part of the tanning process, the bellies perhaps 
being cropped off when struck through. In foreign countries 
it is usual to "round" the hide, or cut the hide into a belt bend, 
untrimmed shoulder and bellies, in the beam-house. The 
theory is that the belting bend represents the greatest value, 
so it should receive the best tanning material and the most 
careful attention. The offal represents less intrinsic value, so 
it can be tanned with cheaper material and by a cheaper 
process. Frequently one of the various rapid-tanning proc- 
esses is used on the offal, and it is not uncommon to finish 
the tannage of the bellies by drumming with strong liquors. 



296 PRACTICAL TANNING 

As offal is not belt leather it will be given no further 
consideration. 

Tanning agents. — In selecting the tanning agent for pro- 
ducing belting leather, the basic material should be chestnut- 
oak wood extract. There is no other material that has so 
many merits, or which will produce a leather having so many 
of the best qualities sought. It gives a good grain, deposits 
enough bloom and filling matter in the fibers of the leather 
to make a solid, firm leather, which is resistant to water to 
a considerable degree, although its tendency is possibly to- 
ward too little pliability. 

On account of the bloom and filling matter deposited, the 
leather made with chestnut-oak wood is sufficiently solid to 
have little stretch and yet be elastic. The tannin of chestnut- 
oak wood is of the pyrogallol group, and hence gives a dur- 
able leather and one calculated to be reasonably indifferent 
to external conditions. The best chestnut-oak wood is one 
of the cheapest tanning materials per unit of tannin on the 
market at present. It is not only cheap, but it is practically 
inexhaustible, in view of the fact that it requires only 20 
years for a chestnut tree to grow to a size at which it may 
be cut. This wood, however, is inclined to produce a rather 
harsh leather. Chestnut liquors develop little acid, and un- 
less artificially acidified by the addition of acid, are inclined 
to make a rather thin leather. It is desirable to combine 
with the chestnut-oak wood some material which will develop 
natural acidity in the yard, obviating the necessity of arti- 
ficial acidifying, and which will modify the harshness of the 
tannage somewhat. In myrabolan is a material which well 
supplements chestnut wood. It gives a mellow tannage, and 
will modify the harshness of the chestnut-oak wood liquors in 
the early stages. It is perhaps the best of the acid-producing 
materials, and will develop enough acid in the liquors so that 
with the aid of the little we get from the chestnut-oak wood 
it will be unnecessary to resort to artificial acidifying. Myra- 
bolan is also a pyrogallol tannin, and so makes a permanent 
leather. It will brighten and lighten the color of the leather, 



BELTING LEATHER 297 

and the color will be little affected by sunlight. The de- 
ficiencies of the myrabolan are offset by the qualities 
of the chestnut-oak wood. Myrabolan, used alone, produces 
a light weight, somewhat spongy leather, which tans slowly, 
We have in chestnut-oak wood and myrabolan, then, a couple 
in which the qualities are complementary; what one lacks the 
other supplies. The chestnut-oak wood comes much nearer 
itself to producing the sort of leather we desire than the myra- 
bolan does, and the mixture used will certainly not be one of 
50: 50; but merely enough of the myrabolan to give the acid- 
ity and mellowness needed. In fact, probably the myrabolan 
will not be introduced into liquors except for the early stages 
of the tanning where the acid is particularly needed for plump- 
ing, and for the mellowness of liquor to prevent drawing and 
harshness of the grain. 

Another material that might be used in place of the myra- 
bolan, and with even better results, is algarobilla. The sup- 
ply of this material is, however, so uncertain that it is diffi- 
cult to rely upon it. If, as is best, myrabolan is used only 
in the earlier stages of the tanning process, it will be desirable 
to mix with the chestnut-oak wood in the latter liquors of 
the tanning process some material to assist at that stage. For 
this purpose a catechol tannin should be used, either hemlock 
or oak bark, preferably the latter. Of foreign materials, either 
mallet (from Australia) or mimosa could be used, preferably 
the former. An ideal tannage would consist of chestnut-oak 
wood extract as the basic material. To this should be added 
oak bark in the later stages, working the liquors down through 
the yard and adding some myrabolan or algarobilla to them 
in the early stages of the tanning process. The chestnut-oak 
wood would constitute more than 50 per cent of the tanning 
material throughout the process, but the exact proportion used 
would be governed by the character of the leather as it came 
along; as with the combination chosen, the proportions could 
be modified to remedy almost any deficiency in the leather, 
and to vary its qualities within fairly wide limits. This is 
one reason why a combination is so much superior to a single 



298 PRACTICAL TANNING 

material; it is much more elastic and yields a much higher- 
grade product. 

Having selected the tanning materials to be used, and hav- 
ing selected them with the idea of making a leather which 
shall have all the qualities mentioned as being so desirable in 
belting, the next step is to see how to use the materials, and 
produce the best results in the shortest time and most 
economically. 

Practical considerations. — Without going into the theory 
of the tanning process, suffice it to say that the underlying 
principles, according to which leather is successfully made, 
are that the tannage shall be started in liquors weak in tan- 
nin, usually liquors through which many hides have previ- 
ously passed, and then be gradually transferred to stronger 
and fresher liquors, so that the last liquor from which they are 
taken is the strongest of all and freshly made. The tannin 
acid, and non-tannin constituents of the liquors must be so 
proportioned throughout that the hide acquires the proper 
condition of plumpness, retains that property, and tans steadily 
and thoroughly. 

The tannin penetrates the hide by diffusion, and as the 
rate of penetration depends on the difference in concentration 
of the liquor in the hide compared with that outside, it is 
apparent that the hides should be placed in liquors of succes- 
sively greater concentration. If, however, the increase in 
concentration is too rapid, the tanning may be rapid but in- 
complete, in some cases even to the extent that the interior 
will not tan at all. Another probable defect from too rapid 
increase of concentration is wrinkled or pipey grain. Difficul- 
ties of this sort are most likely to occur when tannins of 
the astringent type, such as quebracho and mimosa, are em- 
ployed. The difficulty occurs most commonly in the early 
stages of the tanning process before the hide is struck through, 
as, after it is once struck through, it is little susceptible to 
damage from too rapid strengthening of liquors. The more 
mellow the early liquors the less likelihood there is of drawing 
the grain or case-hardening the leather. Inasmuch as old 



BELTING LEATHER 299 

liquors are more mellow than new, both from having the 
more astringent tannins sapped from them and from their 
lower purity due to the increased percentage of non-tannin 
matters, it is almost general practice to top off with strong 
new liquors and work these liquors down through the yard: 
that is, the greener the hide the older the liquor it gets until 
the hide from the beam-house is entered in the oldest and 
weakest liquor. To increase the mellowness of the early liq- 
uors still further, the use of myrabolan has been advocated 
at this stage, which of itself is a very mild tanning material. 
The acid and tannin content of the early liquors must be 
carefully balanced, as too little acid will make a thin, soft 
leather; while too much will make an over-plump leather, 
with cracky grain, inclined to brittleness, also probably poor 
in color. Too much acidity and too much plumpness also 
result in slowing up the tanning process. A certain excess 
of acid in the early liquors is necessary not merely to open 
up and plump the hide, but also to remove the lime which 
remains from the beam-house processes. If the hide is pre- 
pared for tanning with a 3 to 6-day liming and sufficient bat- 
ing to remove surface lime only, it will enter the liquor in a 
fairly plump condition. The surface being free from lime, 
it will take a clear, bright color and begin to tan. The acid 
will diffuse into the hide more rapidly than the tannin, and 
will neutralize the excess of lime. The hide, as the lime is 
neutralized, loses its plumpness and gradually begins to fall 
back or grow soft. This effect becomes more marked as the 
hide is moved ahead into liquors stronger both in tannin and 
acid, until at the end of a week or ten days it is completely 
down and like a rag. In some plants the tendency is to re- 
move all of the lime before entering the yard, and then use 
purer and stronger liquor from the start. A hide then takes 
on plumpness, but this time an acid plumpness ; and as it pro- 
gresses in the tanning process it becomes more and more 
plump and solid, until it has reached the particular condition 
of plumpness that will yield leather of the firmness and pli- 
ability sought. Ability to judge when this condition has been 



300 PRACTICAL TANNING 

reached and to secure more or less plumpness is what makes 
the tanner. Inasmuch as the same apparent result may follow 
from a variety of causes, the aid the chemist can give the 
tanner is by no means inconsiderable, as it will often enable 
the tanner to throw out various hypotheses from the list of 
possibilities. Often, too, chemical analyses may detect a 
change in the composition of the liquors before the effect on 
the hide has become apparent, and so enable the tanner to 
adjust his proportions to the correct balance before the leather 
has gone off. Inasmuch as the lime in the hides neutralizes 
the acid of the liquor, the earliest liquors will naturally be 
lower in acid than the later. The normal variation of the 
acidity, however, would be for the new liquors to be lowest 
in acid, and the acidity to increase steadily to a maximum 
from fermenting action as the liquors age. We find, there- 
fore, in practice, a combination of these two results, that is, 
the sapped or spent liquors are lowest in acid from lime neu- 
tralization, the acidity increases as treatment progresses until 
a maximum is reached where the effect of the lime is lost 
and the result of the fermenting action is greatest, the acidity 
from then on decreasing again. Of course the tannin has 
steadily increased in the liquors, and also the purity. 

As an example, the tail liquor might have an acidity of 0.3 
to 0.4 per cent reckoned as acetic, a tannin content of 0.2 to 
0.3 per cent, and a purity of say 10 per cent; that is, the non- 
tannin constituents would make up 10 times as much of the 
total solid as the tannin. With a liquor such as this at the 
bottom end of the yard, the tannin strength would steadily 
increase as well as the purity and acid, until a maximum acid- 
ity of perhaps 0.7 to 0.8 per cent is reached in a liquor con- 
taining 2 to 3 per cent tannin, and of a purity in the neighbor- 
hood of 30 per cent. From this point on the acidity will 
gradually decrease and the tannin increase, together with the 
purity. The last liquors given the hides will be perhaps 50 to 
60° bk. and contain 8 to 9 per cent tannin. The strength of 
the final layer liquors will depend somewhat on how much 
the hide has been plumped, and on the beam-house conditions. 



BELTING LEATHER 301 

If the hide was rather strongly plumped, or too long in strong 
liquors it will likely produce a leather entirely too solid for 
belting purposes. Both treatments make a tender leather, 
lacking in tensile strength, and likely to crack on the surface 
and break after comparatively short usage; also a leather 
likely to tear at the lace-holes if put together with lacing. 

Tanning of belting leather. — The hides, as they come 
from the beam-house, should be flat and free from wrinkles, 
folds, or marks of any kind. In order that they may not ac- 
quire folds or wrinkles during the early stages of the tanning 
process, it is essential that they be put in the liquor with a 
flat surface, or at least one with no sharp bends to the action 
of the tan liquor. Each hide, morever, must have sufficient 
room to prevent its coming in contact with another hide. 
Where two hides touch, a kiss spot is found; that is, the tan 
liquor does not come in contact with the hide at this spot and 
it fails to color. This is likely to result in a final uneven 
coloring, for unless the hides take the color evenly at the start, 
it is almost impossible to prevent the hide from showing a 
somewhat mottled appearance when finished. 

Rockers. — To give the hide an even color and start the tan- 
nage uniformly, the best practice is to commence in rockers. 
The hides from the beam-house are laid out flat and nailed 
to a stick at the butt end, so that when the stick is lifted 
by its two ends, the hide hangs from it head down vertically. 
The sticks are then put in a frame which is so supported in a 
vat that it can be rocked up and down and the hides with it. 
If whole hides are being tanned, the vats must be suffi- 
ciently deep to allow the hide to hang down straight; but if 
only belting bends or butts, shallower vats may be used. Oc- 
casionally the hides are hung over sticks, but this is not good 
practice, as it often leaves a thin place in the leather, and 
usually a pipey grain where it came in contact with the stick. 

The rockers are best worked in a series of say 10 vats, 
called a "round" because they are arranged in a group with 
no head or tail, and because each vat in rotation becomes the 
head of the round. One vat is emptied of the hides longest 



302 PRACTICAL TANNING 

in the round, and one filled with green hides from the beam- 
house each day. The vat full of oldest liquor is emptied into 
the sewer or returned to the leaches each day, and a vat is 
filled from the handlers each day. The cycle of a round may 
be made in either one of two ways : either the liquor may be 
pumped down or the hides are moved ahead. In the first 
method, the head pit from which the hides are taken today 
becomes the tail pit; yesterday's tail pit liquor is run to the 
sewer, and all the liquors are pumped to the pit next but one 
below in the round, the new head pit being filled with liquor 
from the handlers as mentioned above. In the second method, 
one pit is always empty of hides and full of new liquor from 
the handlers; but instead of moving the liquors, the hides are 
moved two pits ahead each day. As will be seen, the hides 
stay about 10 days in the rockers. 

Handlers. — The hides then go to handlers or suspenders, 
which differ mechanically from rockers only in that hides are 
hung at rest. The handler round is usually larger than the 
rocker, but even though it contains only the same number of 
vats, the hides stay in it longer, generally about 20 days. 
The principle on which it is run is the same as for the rock- 
ers. Occasionally, instead of being run as a round, the han- 
dlers are run on a straightaway, the hides being moved ahead 
and the liquor pressed down ; that is the vats communicate 
with each other so that if liquor is run into the head vat, 
some of the old liquor in this vat is pressed down into the 
next below, which in turn transfers some of its contents to 
the one below it, and so on down the line. Enough liquor 
is removed from the tail pit of the handler section to make 
room for what is run in at the head. 

Instead of using rockers and handlers, the hides are some- 
times rocked throughout the early stages up to the time when 
they are laid away. This has some advantages, and undoubt- 
edly hastens the tanning process ; in fact, one of the quickest 
tannages is dependent for its success on the rocking of the 
hides until the tannage is complete. For making belting 
leather, however, any straight suspension process is not desir- 



BELTING LEATHER 303 

able, as it is practically impossible to hang the hides so that 
they will not bag and draw somewhat into lengthwise 
wrinkles from their own weight. The quantity of wrinkled 
and baggy leather obtained by a straight suspension process 
is too great to warrant its use. The head liquor for the 
handler section is one of the oldest liquors from the yard 
proper, or the layaways to which has been added some fresh 
myrabolan liquor, in order that the necessary acidity may be 
developed in the handler and rocker liquors, and the liquors 
so mellowed. The liquors are worked down through the 
handlers, going then to the rockers, and finally to the sewer. 
Layaways. — At the end of 30 days in rockers and handlers 
the hides are fairly well struck, the color is set, and they are 
fairly well fixed in their condition of plumpness. As they 
hung on the sticks they assumed their most natural position, 
bellying out here and in there, and not at all resembling the 
flat piece of leather which it is desired to make. However, 
had the hides been piled down in these early stages, or had 
they been pressed or pounded to remove wrinkles and bag- 
giness, the plumpness would have been squeezed out, probably 
never to return. This would have been serious to both the 
yield and quality of the leather; flatness having been a rather 
minor issue to this point, attention having been fixed on se- 
curing color, uniform tanning, and the right degree of plump- 
ness. At the end of the handler stage, however, the hides 
are sufficiently well set so that they may be piled down and 
flattened out moderately without undue loss of plumpness. 
If the flattening process is deferred too long, the wrinkles 
become so fixed that further remedies can only modify and 
not eradicate them. At this stage, therefore, the hides go to 
the layaways. These are vats large enough to permit the 
hide being spread out flat. They are laid down with a layer 
of tan bark or some inert material between each successive 
hide so that the liquor with which the vat is filled may come 
in contact with all parts of the hide. In the early days of vat 
tanning, when only what would be now called very weak liq- 
uors were obtainable, the layer of tan bark between the hides 



304. PRACTICAL TANNING 

was thick, and was used as much to supply tannin as to sepa- 
rate the hides. With the use of the present-day strong liquor, 
bark has become unnecessary as a source of tannin, and it is 
used merely to keep the hides apart and let the liquor get at 
them. This is not always true in sole-leather tannage, where 
valonia and similar materials are used 'for dusting. The 
early layers are for a fairly short time, and gradually increase 
in length and strength of liquor as the hides become more 
thoroughly tanned. A 100-day layaway series, for instance, 
would run 3, 5, 7, 9, 12, 16, 21, 27 days per layer, the pack 
being hoisted at the end of each period and laid away in a 
different and stronger liquor. Some tanners prefer to use a 
fewer number of layers, allowing the pack to remain in each 
layer for a longer period. At each hoisting the hides are very 
carefully pulled and stretched, and piled so that all wrinkles 
and bagginess, hip pockets, etc., will be flattened out, and the 
hide so far as possible put in such a condition of flatness, 
that when laid on a level floor it will touch at all points. 

The last four or five, possibly six, liquors are fresh leach- 
house liquors; the earlier ones are those from which one or 
more packs have been drawn, so that they have mellowed 
and gained in acidity. These liquors are gradually worked 
down through the yard, through the handlers and rockers 
to the sewer. All the layaway liquors are not so worked 
down and out. some being returned to the leach-house to be 
strengthened and freshened; and, as previously described, the 
liquor run to the handlers is strengthened by fresh material, 
notably myrabolan liquor, to develop acid. In some tan- 
nages other materials are frequently added at this stage to 
secure some special color, mellowness, or other quality. The 
strength of these layer liquors depends on the tannage desired, 
but in general for belt, leather the strongest liquor used would 
not run over 40 to 60° bk. Not many years ago, a 45° liquor 
would have been regarded as too strong, but with a better 
knowledge of the tanning process, and the growth of the use 
of extracts, liquors as high as 120° bk. are not at all uncom- 
mon, though not suited for making belting leather. As de- 



BELTING LEATHER 305 

scribed, the tanning process has required 130 days, an average 
time, but both longer and shorter being in use. 

Bleaching. — It is generally held that tanned hide must be 
allowed to dry before being curried, in order to "set" the 
tannage. It is therefore common practice, whether the leather 
is tanned in the same factory where it is to be curried and 
made into belting, or whether it is tanned to be sold in the 
rough as a market butt, to give it a preliminary crude finish 
such as is seen on ordinary rough leather. This finish con- 
sists of washing, bleaching, oiling, and drying. Inasmuch as 
rough belting butts are sold by the pound, the usual tannery 
washing is the least that will conduce to a satisfactory ap- 
pearance, and enable the leather to undergo the usual physical 
examination to which buyers subject it.' Of course, when the 
leather is produced for local consumption, the washing at 
this stage will be sufficiently thorough to obviate the need of 
the further washing usually given leather before the currying 
process. Bloom is left on leather to be sold in the rough, but 
this must be scoured off before the currying is begun or as a 
part of the currying process. Briefly, the washing consists of 
soaking in water at 110 to 120° F., or warm weak liquor, and 
brushing off the surface dirt with a hand brush or by machine. 
Some tanners use an old weak sour liquor for soaking, claim- 
ing to get less loss of weight and some improvement of color. 
Color is the tanner's bugbear. , If color and quality were syn- 
onymous, there would be some excuse for the stress laid on 
the former, but frequently leather of good color is poorest in 
quality, hence the tanner feels compelled to make his leather 
present as attractive an appearance as possible. Good looks 
is the only excuse for bleaching, and when' one considers the 
damage — both present and future — which the leather suffers 
in the bleaching process, it will be seen that this quality is 
dearly bought. The bleaching of the leather is usually ac- 
complished by soaking or wheeling the leather in a bath of 
sal-soda or borax, and rinsing, and placing it in a bath of 
some dilute acid — generally sulphuric or oxalic. After this 
bath the leather is thoroughly rinsed in clear water to remove 



306 PRACTICAL TANNING 

the acid. Unfortunately, the total removal of the acid is 
very difficult, and some remains in the leather. As sulphuric 
acid acts destructively on all organic material as long" as it 
is present in a free state, a gradual deterioration — rotting of 
the fiber — is bound to occur in leather containing any of this 
free acid. A combined washing and bleaching process, which 
seems less objectionable than many of those in use, is to soak 
the hides in a liquor made from one of the heavily sulphited 
extracts. In fact, extracts of this type are on the market 
under the name of bleaching extracts, and give fairly satis- 
factory results. If, however, the hides are properly prepared 
in the beam-house, and the liquors rightly proportioned, there 
is no reason why leather cannot be made, which, after care- 
ful washing, will give a sufficiently good color without 
bleaching. 

Oiling. — After washing and bleaching comes oiling, which 
consists in covering the wet leather all over with a heavy coat- 
ing of Newfoundland cod-liver oil. After oiling, the leather 
is ordinarily 'piled-down over night to give the oil a chance to 
strike in somewhat, and is then hung to dry on hooks or 
clamps fastened to the butt end. 

Drying. — This process • demands careful attention if best 
results as regards color, flexible grain, etc., are to be secured. 
It was a rather uncertain process as far as results were con- 
cerned when the leather had to be dried under ordinary atmos- 
pheric conditions, but in these days of steam heat and venti- 
lating fans there is no real reason at all for failure to secure 
as certain and regular results in the drying as in any other 
part of the leather-making process. The essentials of suc- 
cessful drying are to start the process in a cool, moist air, and 
increase the temperature and dryness of the air with the dry- 
ing of the leather. When the leather has been dried, it may 
be trimmed somewhat, rough corners cut off, etc., and is then 
ready for the market. 

Currying. — While most belt-makers probably do not tan 
the leather they use for making into belting, they nearly all 
curry the leather. They buy market butts in the rough, curry 



BELTING LEATHER 307 

them, and make them into belting. Currying may be defined 
as introducing grease into leather and giving it such a finish 
as will best adapt it to the purposes for which it is to be used. 
As a matter of fact, currying, if properly performed, is really 
making a combination-tanned leather out of the oak leather 
by giving the latter a supplementary oil or fat tannage. In 
order that the fat may produce this result it must be deposited 
on the minute fibrils which make up the fiber bundles consti- 
tuting the leather. The fibrils, having already been separated 
by the vegetable tanning process, the fat may easily be de- 
posited on them ; but an essential condition for the successful 
deposition of the fat is that it be introduced into the leather 
while the stock is wet. As the water dries out from between 
the fibrils, the fat replaces it and brings about the secondary 
oil tannage, which renders the leather more pliable, more 
resistant, and permanent, and of increased tensile strength. 
Inasmuch as the grease is introduced into the leather when it 
is wet, the first step in the currying process would seem to be 
to wet-back the leather. 

The wetting-back of the leather is, however, not ordinarily 
done merely as a preliminary operation to putting- the grease 
into the leather, but is a clearing process intended to remove 
superfluous tannin, bloom, etc. As the washing which the 
rough leather usually receives at the tannery is as little as is 
consistent with a satisfactory appearance, the belt manufac- 
turer finds that it improves the quality of his leather to remove 
some of the excess tannin left in by the tanner and replace it 
with grease. He therefore gives the leather a rather thorough 
washing, its completeness depending on the currier's previous 
experience with the leather, or his judgment of how much is 
needed. 

Scouring. — If the tannage be inclined to excessive solidity 
and firmness, the leather will be soaked to soften it somewhat 
and then drummed with warm water. This treatment will 
last from 10 to 30 minutes, perhaps with no change of water, 
but probably with a constant stream of warm water entering 
the wheel; in extreme cases, the leather may be drummed in 



308 



PRACTICAL TANNING 



\a weak solution of borax, then in clean warm water. The 
drumming is ordinarily followed by a scouring process, needed 
particularly in the case of leathers with much bloom. This 
scouring is sometimes done on a Vaughn machine, a stream 
of water being run on the revolving roll and the leather; but 
it is perhaps done more successfully on a Fitz-Henry machine. 
A stream of water is run on the part of the leather worked 
on by the stones of the Fitz-Henry machine, and the move- 
ment of the stones under these conditions scours the leather 
satisfactorily. If the tannage is lighter, it may be sufficient 




Figure 87. — Currier's knife. 

merely to soak the hides and work them out on a Vaughn or 
Fitz-Henry; or even — if the leather carries little bloom — after 
the soaking, merely brush the leather by hand or machine. 

The belt butt, usually after the washing, but sometimes 
before, is cut into a belt bend and shoulder. While the best 
part of the shoulder may sometimes be used for a cheap 
quality of belting, our interest is in the belt bend; but the 
process of currying the shoulder for belting is similar to that 
for currying the belt bend, save that more and somewhat dif- 
ferent treatment is required to work out wrinkles as much as 
possible. The belt bend is at this stage cut into three pieces — 
a center and two sides — the divisional cuts being made par- 
allel to the backbone and at equal distances from it on either 
side. There is a growing tendency to finish and stretch belt 
leather in the whole bend rather than in center and sides. 

Skiving. — This is the removal of superfluous flesh, etc., 
from the flesh side of the leather. It used to be done almost 
entirely over the beam with a knife with a turned edge (fig- 



BELTING LEATHER 309 

ure 87), but this is now done by the belt-knife splitting 
machine! Still another method of skiving, wh.eh.ts largely 
used at present, is by the whitening machine (figure 88). 
Whitening is done at a later stage, but at whatever stage per- 
form d its object is to give a clean, smooth back to the eather 
wTth no superfluous flesh. If, for instance, the leather ts 




Figure 88.-Whitening machine u^d for cleaning- 
up flesh side of various kinds of leatner. 

to be used for a double belt, that is, one made of two thick- 
1 es of leather cemented together flesh-to-flesh, it .*£ not 
be possible to cement the leather so that it wou d hang to 
gether under the conditions of service if any loose or super 
fluous flesh remained on the leather. s „hiected 

Hand stuffing.-^, next process the leather »**£•£ 
to is dependent upon the particular mode o . tiffing o be 
employed, that is, the way in which grease ? shabby put nto 
the leather. There are three methods in use for tuffing bekmg 
leather namely, hand stuffing, wheel stuffing, and hot stuffing ' 
The first is the oldest method, and is still preferred by many 
hirers. The leather, after skiving is amped ba* 
and Diled down to even up and temper, that is, before apply 
£ the stuffing it is desirable that the leather should be in 



310 PRACTICAL TANNING 

as uniform a condition of wetness all over as can be attained. 
In this case, the grease will penetrate more evenly, and yields 
a much more uniform and satisfactory piece of leather. The 
currier therefore wets the leather where it seems dry and 
then piles it down so that parts of the leather having too 
much moisture will give up some to the dryer parts, and vice 
versa. After tempering, the leather is set, usually either by 
hand or on a Vaughn machine. If by hand, the leather is 
spread out on a table and carefully worked out by a slicker 
until it lies perfectly flat on the table with the edges as 
straight as possible and the grain smooth. If by a Vaughn 
machine, it is gone over several times with the roll until it 
is as flat and smooth as possible. After setting, it is given 
the grease or stuffing. This is applied usually to the flesh 
side alone, the grain side getting a coat of refined Newfound- 
land cod-liver oil. There is little variation in the composition 
of the hand-stuffing of dubbin used in different factories. 
It is generally made by melting together 2 parts of oil and 5 
parts of tallow, if the tallow be soft, or 1 part of oil and 4 
parts tallow if it be hard. These formulas are varied 
slightly according to the season of the year, more oil and 
therefore a softer dubbin being used in cold weather and the 
reverse in warm. After melting, the mixture is stirred con- 
stantly while cooling so as to produce a smooth salve-like, 
homogeneous mass. This dubbin is applied with a swab to 
the flesh of the leather so that it makes a smooth, even coat- 
ing, the thickness depending on the currier's knowledge of 
how much grease the leather will absorb, and not be discolored 
or look greasy. Only the oily constituents of the dubbin 
enter the leather, the harder components of the tallow, stear- 
ine, and palmitin being left as a white coat on the surface. 
After the leather has been given its coating of grease, it is 
hung in a moderately warm room with a good circulation of 
air, and allowed to dry. If too much heat is applied the 
leather becomes black and greasy, the grease not penetrating 
into the fibrils; but if too little heat, drying requires an ex- 
cessively long time and the leather is likely to mildew. When 



BELTING LEATHER 311 

properly carried out, the oily portions of the dubbin enter the 
leather as it dries, giving it a rich mellow feeling, and leaving 
it a good color. When the leather is dry, nothing but a dry 
white scale showing no oiliness should be left on the back, 
The leather is now taken down, wet-back once more, and 
piled-down, and is then ready to stretch. 

Wheel stuffing. — The leather is washed and skived as in 
the hand-stuffing process, but the division of the belt bend into 
a center and sides is usually deferred until later. After 
skiving, the bend is wet-back and piled-down to temper. For 
wheel stuffing, this wetting-back is a most important opera- 
tion, and the success or failure of this treatment depends 
more on the preparation of the leather than on anything else. 
The wetting is usually entrusted to one man who makes a 
specialty of that work, and he must be an artisan of rather 
more than ordinary judgment. For wheel stuffing, the leather 
must not be wet uniformly, but the softer and spongier parts 
of the leather must be distinctly wetter than the firmer parts, 
otherwise they absorb so much more grease that they appear 
very black and greasy in the finished leather. The usual test 
to find out whether leather is in proper condition for stuffing- 
is to bend it over and see if this forces out water in fine drops; 
but evidently there will be a difference in behavior between 
the softer and firmer parts of the leather, and the precise 
action can be learned only by experience. 

The leather which has been wet-back is usually allowed 
to lie in a pile, covered with wet bags or protected in some 
similar way, until it begins to heat up by fermenting action. 
It is then touched up by the man at the wheel, the spots that 
seem at all dry being given a little more water, and thrown 
into the wheel as quickly as possible to get the benefit of the 
heat in the leather. The old-time wheels were simply heated 
by running in live steam before the leather was put in, and 
the heat retained by the wheel depended upon to keep the 
leather and grease warm. The better modern practice is to 
use a wheel connected through the two hollow trunnions with 
a fan and steam coil, so that hot air can be run in and out 



312 PRACTICAL TANNING 

of the wheel throughout the drumming process. The wheel 
contains shelves or pins on the inside, so that the leather is 
carried up by the wheel as it revolves until it is no longer 
held, when it drops back to the bottom of the wheel to be 
picked up once more. The warm leather having been put 
into the wheel through a door in the side or rim, the hot 
melted grease is added, the door closed, and the wheel started. 
The temperature of the wheel inside is kept at about 120° F. 
The stuffing grease used in the wheel is harder and less oily 
than that used for hand stuffing. If of tallow and cod oil, 
a much greater excess of tallow is used, and frequently oleo- 
stearine is added to the mixture to produce a still harder 
mixture. For instance, one formula used for belt leather 
consists of 9 parts good tallow to 1 part refined cod oil; an- 
other and harder, 75 parts tallow, 9 parts stearine, and 16 
parts cod oil. As in hand stuffing, the formula used is varied 
in accordance with the season of year and the known capac- 
ity of the leather for carrying grease. An average leather 
can carry 12 per cent of grease similar to the above mixtures, 
calculated on the we1^ weight of the leather as prepared for 
stuffing. It will usuahy require about an hour to work this 
quantity of grease into the leather. The rolling, tumbling, 
and pounding given the leather in the wheel gradually works 
the grease in among the fibers of the leather, but it probably 
is not really deposited on the fibrils themselves until the leather 
dries. During the last part of the drumming in the wheel, 
the door of the machine is frequently removed to cool the 
leather somewhat and set the grease, and as the leather is 
finally removed from the wheel it is piled down for at least 
24 hours, being turned over during this time to prevent ex- 
cessive heating, in order to give the grease still further oppor- 
tunity to fix itself permanently in the leather. 

If this were not done, far too much of the grease would 
be worked out of the leather during the various setting proc- 
esses which now follow. The wheel-stuffed leather, which 
was carried along as a belt bend, is usually set on a Fitz- 
Henry or Turner serial table machine (figure 89), though it 



BELTING LEATHER 313 

is sometimes still set by hand. The former, from its 
construction, gives results much more nearly approaching 
hand setting; in fact, it is a very interesting sight to watch 
an experienced operator take a baggy bend and gradually 
work out the bag until the bend lies smooth and flat on the 
table, a procedure often requiring considerable skill. The 




Figure 89. — Serial table setting-out machine. 

Turner machine is very simple, and requires no special skill 
to operate. The bends are spread over the edge of a moving 
table which passes between revolving rolls. These rolls press 
the leather down, spread and flatten it, and set it out fairly 
well, if the leather was in reasonably good condition to start 
with, that is, fairly flat and not too hard and heavy. In the case 
of a really bad bend, however, hand-setting or the Fitz-Henry 
machine must be resorted to. The great advantage of the 
Turner machine is in the increased amount of work it can 
do. After the belt bend has been set out it is cut into a 
center and sides, if desired, or carried through as a whole 
bend, and is worked out still further on the Vaughn machine 



314 PRACTICAL TANNING 

to give a smooth grain free from wrinkles and make a more 
compact piece of leather; then oiled on the grain, and is ready 
for the stretching process. 

Hot stuffing. — There is one more method, namely, the so- 
called hot stuffing. It is rather curious that if very hot grease 
be put on a piece of leather which contains any appreciable 
amount of moisture, it will burn it, making it brittle and of 
no strength. If, however, this same hot grease be applied to 
an absolutely dry piece of leather, it exerts no harmful effect. 
The hot-stuffing method then consists in placing the belt bends . 
in a dry room where they are heated until all moisture has 
evaporated, and either laying them on a table and pour- 
ing hot grease over the flesh or grain, or both ; spreading it 
by a brush so long as it is absorbed by the leather, or actually 
dipping the whole bend into a tank of melted grease, and 
allowing it to remain until it has absorbed all the grease possi- 
ble. In either case the grease may be 200° F. or over. In 
the second case, the leather, after removal from the tank,, is 
hung in a hot room to drip and permit surface grease to melt 
off, after which it is thrown into cold water. The bends 
piled on the table are thrown into cold water as soon as 
filled. 

The grease put into the leather in this way does not "com- 
bine with the leather, coating the fibers and bringing about 
a beneficial grease tannage, but merely serves as a filler. Be- 
fore the leather filled with grease by this process can be said 
to be really stuffed and curried, a way must be found to 
make the grease come into intimate contact with the fibrils of 
the leather. This is accomplished by wetting the leather and 
allowing it to dry, when, just as in the hand and wheel- 
stuffing processes, the grease follows the water into the in- 
most fibrils of the leather and brings about the grease tannage. 
The hot-stuffed leather, being saturated with the grease, is not 
readily wet-back, consequently simple soaking in water will 
not suffice. The leather is therefore put in a wheel and 
drummed with water until it has become soft and wet through. 
This is really a drum-stuffing process reversed. In the one 



BELTING LEATHER 315 

case, wet leather is put in and drummed in grease ; in the other, 
creasy leather is put in and drummed in water. At the end 
of the drumming process the leather must be put through some 
sort of cleaning process to remove the grease from the sur- 
face and so yield a product of good appearance. The hot- 
stuffed leather, stuffed on the table by having hot grease spread 
on the flesh side alone, may be brought through in a condi- 
tion where the grain is clear and free from grease and so need 
no bleaching; but this is doubtful policy, as it may have the 
grain side lacking in grease and likely to finish harsh and 
dry. There are a large number of bleaching processes in 
use, some using the regular soda and acid bleach, which is 
likely to be less harmful at this stage on account of the con- 
siderable amount of grease in the leather. Some makers use 
a little borax, soda, or soap to cut surface grease. In some 
cases drumming with sumac leaves is found to work satis- 
factorily, and this latter method would seem to have less ob- 
jectionable features than any of the others. After the wheel- 
ing and bleaching processes, the belt bend is handled the same 
as the belt bend in the drum-stuffing process. It is piled-down, 
set, cut into center and sides, worked on a Vaughn machine, 
oiled on the grain, and stretched. 

There are advantages and disadvantages connected with 
each mode of stuffing. For instance, it is impossible to over- 
load the leather with grease by the hand-stuffing process ; but 
on the other hand, it is impossible to put into the leather any 
of the harder greases which give leather a peculiarly mellow 
and substantial feel, as well as making it more permanent 
and resistant. 

Stretching. — This process and finishing are the same for 
all the leather, whether hand, wheel, or hot-stuffed. The 
idea underlying the operation is that leather, being a fibrous 
material, will, when subjected to stress, "give" more or less 
and stretch out, becoming longer. If this stretching takes 
place after the leather has been made up into belting and 
put on a machine, the belt may soon become so loose that 
it will fail to drive, necessitating a shut-down until the belt 



316 



PRACTICAL TANNING 



can be shortened; so the leather is stretched to remove most 
of the give, and that the trouble from the belt stretching on 
the machine may be lessened. It is not desirable that this 
preliminary stretching be carried to the utmost limit, as this 
undoubtedly weakens the leather and reduces its term of 
service. 

The stretching process is simple, and consists in fastening 




Figure 90. — Heavy rolling-jack. 

the ends of the piece of leather in clamps, one of which is 
securely fastened at the end of a rectangular frame or board, 
the other of which can be moved, and by a tooth-and-dog ar- 
rangement fastened at any desired point. The frame and all 
is then put in a machine which grips the two clamps, and suit- 
able mechanism pulls the free clamp slowly away from the 
fixed one, thereby stretching the leather. When sufficiently 
stretched, the dog is allowed to drop into place, and the frame 
removed from the machine and hung in a room where the 
leather can be left to dry out in the frame in its stretched 
condition. The leather, when removed from the frame, if it is 



BELTING LEATHER 317 

good leather of reasonable elasticity, springs back somewhat 
and loses some of the stretch given it. Moreover, on ac- 
count of the unnatural condition of the fibers when dried, the 
leather has a rather stiff and bony feel. It is therefore worked 
on a heavy rolling- jack (figure 90) on the flesh side, which 
mellows the leather, removes the stiffness from it, and gives 
it pliability. If a dull finish is desired on the grain, the 
leather is brushed under a rotary brush; and if a glossy finish, 
the leather is passed on a glazing-jack, after which it is ready 
to be made into belting. 

The question whether a leather belt should be run with the 
grain or flesh side next to a pulley has been much debated, 
and tests of the power capacity of each side were recently 
made by the Leather Belting Exchange at Cornell University, 
under the direction of R. F. Jones. The test covered two 
months. Five 4-inch single belts, 30 feet long, of different 
makes, were used; and all were thoroughly "run-in," or had 
reached a condition of constant capacity when the records were 
taken. The method was to take horsepower readings from 
the belts, first when running on the grain side and then on the 
flesh side, the power being gradually increased until about 4 
per cent slip had been reached. A summary of all the tests 
was clearly in favor of the grain side from the standpoint of 
transmission. Under reasonable shop tension, the flesh side 
will average only 50 to 60 per cent as much power as the 
grain side; but the running is more uniform than the grain 
side. 



CHAPTER XI 

STRAP, WELTING, BAG, CASE, AUTOMOBILE, AND 
HARNESS LEATHER 

Strap leather. — In this chapter only a general outline is 
given of the various operations, as the details involved have 
been already covered in previous chapters. 

Stock. — The stock should be green-salted packer steers and 
cows, ranging from 50 to 70 lb. ; South American frigorificos, 
or green-salted Chinas. These hides should be free from 
grubs, cuts, brands, and scars. 

Soaking. — The trimmed stock, either as hides or sides, 
should be washed in the mill for 15 minutes with running 
water, toggled together, and then placed in the soaks, fresh 
water being used. After 24 hours the hides should be reeled 
to a second soak for another day. 

Depilating. — For this grade of leather it is very essential 
to conserve as much hide substance as possible, and in order 
to do this, very old lime should be avoided and the time of 
treatment reduced to the minimum. A process which gives 
exceptionally good results is as follows : The soaked stock 
is reeled into a tail-lime liquor which has been pressed down 
from the head pit and to which has been added a half-pound 
of crystal sulphide for each side. Having established the 
liming process, half of the tail liquor is discharged and its 
place is taken with well plunged liquor from the pit above. The 
sulphide is added to the tail liquor. As the tail lime is dis- 
charged, fresh lime should be added to the head pit. 

Unhairing. — The depilated hides as they come from the 
warm pool should be spotted on the floor for white hair, and 
then unhaired on either a Leidgen, Whitney, or Turner ma- 
chine. They should then be fleshed on the machine, and fine- 
haired on the beam if necessary. The unhaired and fleshed 
stock should be washed in a slush-wheel or paddle. 

Bating. — The bating should be done with oropon XX. In 

318 



STRAP, BAG, AND HARNESS LEATHER 319 

using this bate, start the paddle with 12 oz. of oropon for each 
100 lb. of stock, discharging a third of the liquor each day 
and making up with 8 oz. for each additional 100 lb. At 
the end of the week, completely discharge the old bate and 
start fresh on Monday. The temperature of the bate should 
be about 90° F. when the pack is entered, and the stock 
should be bated through before removing from paddle. 

Washing. — The bated stock should be thrown into the pad- 
dle-wheel and washed with cold running water for half an 
hour. 

Rockers or stick pits. — The washed hides should be placed 
on sticks, preferably using a rocker system, or some other 
satisfactory method of agitating the liquor. The tail liquor 
should stand at about 8° bk. and contain about 0.31 per cent 
of acid. The density of the liquor should increase gradually 
to 15°, and should be pressed forward each day for 20 days. 
It will be understood that various combinations of tanning 
material could be used, but it is suggested that a combination 
of 33 per cent hemlock, 33 per cent ordinary quebracho., 31 per 
cent of chestnut bark, and 2 per cent of myrabolan be em- 
ployed. In order to prevent an accumulation of soluble non- 
tans, it is desirable to discharge at least one out of every five 
tail rocker liquors ; the other four may be returned to the leach 
or extract mixer. 

Splitting. — One of the most important factors in making 
strap leather is in connection with the splitting. If the stock 
is over-tanned before splitting, it is likely to be weak. When 
in proper condition the hides should be well struck, but should 
show yellowish through the center portion. 

Layaivays. — From the rockers or stick pits the hides are 
jacked and split to gage, and the grain placed in the layer. 
The tail-layer liquor should stand at 20° bk. and the head layer 
at 28°. The stock should be handled forward after 24 hours, 
again after 3 days, at the end of 7 days, at the end of 11 days, 
and removed at the end of 2 weeks. The same combination 
of liquor may be used as in the rockers except that the myrab- 
olan should be eliminated. A slightly better combination, 



320 PRACTICAL TANNING 

however, consists of a mixture of 50 per cent ordinary que- 
bracho, 25 per cent chestnut, and 25 per cent hemlock. 

Bleaching, — As it comes from the layers the stock is washed 
slightly and then stripped with a small amount of borax, say 
| per cent on the weight of the stock, running for 10 min- 
utes ; the borax solution is removed and the alkaline condition 
eliminated by running for 10 minutes with |- per cent of sul- 
phuric acid. It should be understood that both the borax and 
sulphuric acid must be very dilute. 

Re-tanning. — To the bleached stock still in the mill, enough 
water is added to float it, and then 2 per cent of dry sumac 
is introduced. The stockis milled with the sumac for half an 
hour, well washed, and passed through the Quirin press. 

Stuffing. — The well-set stock from the press is again placed 
in the mill and heated with hot air. When warmed through, 
a mixture of 3 lb. of stearine and 8 lb. of tallow for each 
100 lb. of stock is melted, and at a temperature of 130° F. 
is added to the leather in the mill. The mill is now run for 
half an hour to absorb all of the fat. From the drum the 
stock is piled-down for several hours to set the grease. 

Setting. — When the grease has become fixed, the stock 
should be dipped in cold water, and then set out on the ma- 
chine, preferably the Fitz-Henry. The stock should next be 
piled-down over night, and then set by hand, using a dubbin 
of 3 parts of tallow to 1 part of cod oil on the flesh. The 
leather should again be piled-down over night and re-set by 
hand without application of dubbin. 

Tacking. — A light coat of cod oil should finally be applied 
to the grain and the stock tacked. 

Whitening and snuffing. — When dry, the sides are removed 
from the boards and whitened on the flesh side. They are 
then snuffed by hand, although some success is being ob- 
tained by using a special shaving machine and emery wheels. 
To the flesh side a solution of Irish moss or lissom extract 
should be applied, and the stock rolled on the flesh while yet 
damp. 

Finishing. — To the flesh side, a solution of either dextrine, 



STRAP, BAG, AND HARNESS LEATHER 321 

lissom, or flaxseed liquor containing an acid yellow, should be 
applied. This mixture produces the russet shade. When dry, 
the stock should be smooth-plated and given a tallow finish 
on the grain. This tallow finish could consist of either pressed 
tallow or stearine made into an emulsion with soap. These 
finishes may also be purchased on the open market. When 
the stock is perfectly dry, it should be brushed on the machine 
and is ready for use. Some equipment manufacturers prefer 
to receive the leather before the tallow finish has been brushed, 
as it protects the leather during the handling through their 
shop. The tallow finish has an advantage over shellac finish 
in that it is more waterproof. 

Goodyear welting. — The better grades of welting are made 
from plump hides weighing 50 to 60 lb. each, and tanned ex- 
pressly for welting. Welting is also made from the shoulders 
of belting butts, but such leather is likely to be harsh and 
brittle, and not as satisfactory as that made from upper 
leather. The hides are limed thoroughly and bated down low 
to give a fine grain. 

Tannage. — The tanning should be effected fairly slowly and 
the tannage should be mild to prevent drawn and rough grain 
from too strong liquor. Any good upper-leather tannage is 
suitable for welting. A combination (2 to 1) of quebracho 
and .hemlock extracts produces good leather. The sides are 
suspended in weak coloring liquor for 24 hours and are then 
transferred to stronger liquor, which is strengthened from 
day to day until the sides are well struck through. Chestnut- 
oak wood, as well as oak and hemlock, also makes good welt- 
ing leather. Leather tanned in weak liquors finishes softer and 
tougher than that rushed through strong liquor. The hides, 
when well struck with the tan, are put in the press and made 
ready to be split. Before being split, they are, however, 
cropped and the bellies sent back to be re-tanned. The backs 
are split 6 to 8 oz., according to the weight desired, and are 
then put into a drum and re-tanned with strong gambier liquor. 
Sumac should not be used, as it has a tendency to make the 
grain coarse. The next process is bleaching to remove the 



322 PRACTICAL TANNING 

stains from the splitting machine. The leather is run in the 
drum for 30 minutes in a solution of 6 lb. of borax in 40 
gallons of water at 100° F. After this, the leather is washed 
in clear water to remove the borax, it is then milled in a solu- 
tion of sulphuric acid, using 1 pint of acid in 40 gallons of 
water, and running the leather in it 20 minutes. The leather 
is then washed in clear water and fat-liquored. 

Any good fat-liquor will do, but better results seem to be 
secured with the use of neat's foot oil and chip soap. The 
leather is fat-liquored, dried, and- sammied, and set out thor- 
oughly. A light coat of cod oil, mixed with 25 per cent of 
paraffin oil, is then given the grain ; the leather is next turned 
over and struck out on the flesh, a light coat of fat-liquor 
being then applied to the flesh, and the leather hung up to 
dry. When partly dried, it is taken down and re-set with a 
heavy slicker, then dried and put into pres's. It is not rolled, 
nor is any finish applied. If the work is carefully done, the 
grain has a light, clear color which readily absorbs any stain 
or color that may be applied. 

Rough leather of soft tannage makes good welting when 
finished in this manner, but it must be firm and pliable, and 
not harsh and brittle. 

The shoulders of the hides, the butts of which are made 
into belting, cut from the hides before they are tanned, are 
largely used as welting. The shoulders, after having been 
tanned, are run through the splitting machine and leveled. 
They are then bleached with sulphuric acid after a borax bath, 
as described, washed with clear water, scoured, hung up to 
dry, and when in condition, are rolled on the sole-leather roller. 
A coating of oil is next given them, and they are then dried 
out, receiving no other finish. This shoulder welting is never 
as good as that made from the backs of upper stock treated 
in the manner previously described. An oak tannage is pre- 
ferred to other tannages for shoulder welting. 

Bag and case leathers. — The first essential in the manu- 
facture of bag and case leathers is good hides, preferably 
green-salted, which are clear on the grain and free from 



STRAP, BAG, AND HARNESS LEATHER 323 

butcher cuts on the flesh side. When the hides have been se- 
lected, trim off the heads and shanks and put the hides into 
clean soft water. The best way to soak them is to suspend 
them in the water for 24 hours ; then take, them out or run 
off the water and fill the vat with fresh water, and soak 24 
hours longer. Then split into sides, taking care to keep the 
backs straight. Five pounds of borax, dissolved and added 
to 1,000 gallons of water, helps to soften and cleanse the 
hides. After having been split into sides, the hides are 
fleshed, when they are put into clean cold water over night 
and the next day into the lime, which usually requires 6 or 7 
days. The hides are then washed and bated by using any 
one of the several bating processes that have previously been 
described. The hides require a clean bate to prevent staining, 
and need to be well bated to produce a soft and clear grain. 
They may then be either pickled or drenched. 

Tanning. — Hemlock and quebracho extracts used in 33 : 66 
proportion make an excellent tanning process for bag and case 
leathers. The sides are nailed on sticks and suspended in a 
weak coloring liquor for 24 hours. This produces plumper 
leather than a paddle-vat. The sides are then put into a liquor 
of about 10° bk. strength, and each day the liquors are bet- 
tered until they are about 30°. When well struck through 
with the tan the sides are pressed and split. The grains may 
be re-tanned in a drum with hemlock-quebracho liquor, and 
then colored and finished. Tanning with hemlock and re- 
tanning with a combination liquor is effected as follows: 
The sides are tacked on sticks and hung in a 7° hemlock liquor. 
They are handled every day for three days, and the strength 
of the liquor is gradually raised to 10° and then to 12°. 
After being in a 12° liquor for 24 hours, the sides are put 
into a combination liquor made of chestnut-wood extract and 
quebracho extract. The strength at first is 16° ; but this is 
gradually raised to 20°, taking 16 days to do it. The leather is 
next pressed and split, and the grains are then re-tanned. The 
re-tanning liquor should be 3 parts quebracho and 1 part gam- 
bier of about 26° strength, and the leather milled in it one 



324 PRACTICAL TANNING 

hour, then placed in piles for 24 hours, after which it is in 
condition to be bleached and colored. 

Another good tanning process consists of two-thirds hem- 
lock and one-third oak-bark. The hides are first colored in 
a sour liquor, then put into the tan liquor of 7° and handled 
each day, the liquor being strengthened until it is 10 or 12°. 
When well struck with the tan, the hides are pressed and split. 
Re-tanning is done with either quebracho and sumac, or with 
quebracho and gambier. If the former is used, the liquor 
should be 20°, two-thirds quebracho and one-third sumac. 
Running the leather in this liquor for an hour accomplishes its 
re-tannage, after which it is ready for coloring and finishing. 

It is sometimes advisable to drum the sides in a solution 
of borax, and then in an oxalic acid liquor after they are 
split and before re-tanning, in order to clear and bleach them. 
The leather is first run in a borax solution for 20 minutes and 
then washed, after which comes a solution of 2 lb. of oxalic 
acid in 15 gallons of water for 10 minutes, finally washing 
free of acid and re-tanning, 

The usual practice, however, is to bleach leather which re- 
quires it, after it is re-tanned. It should not be pressed too 
hard for splitting, since the more moisture there is in the 
grain when re-tanned the better the results will be. When 
leather is pressed dry for splitting, the grains should be milled 
in weak liquor before they are re-tanned, and this extra mill- 
ing prepares them for the re-tannage. More rapid and thor- 
ough penetration results by adding 1 quart of sodium bisul- 
phite to each 6 gallons of re-tan liquor. Excellent leather is 
made by tanning the sides in a one-bath chrome process, then 
washing and re-tanning, the latter being done with quebracho 
and chestnut-oak extracts" in the proportion of 3 parts of the 
former and 2 parts of the latter. The liquor should be 12° 
bk. at the start, strengthened to 18° the next day, and to 24° 
on the third day. Each night the hides should be taken out 
of the liquor and piled down until the next morning, and then 
put into the strengthened liquor. After having been re- 
tanned for three days, the sides are piled down until the next 



STRAP, BAG, AND HARNESS LEATHER 325 

day, then pressed and split. The well-washed hides, after re- 
tanning, should be stuffed with a mixture of equal parts of 
degras and cod oil emulsified with a soluble oil, and hung 
up to dry. The dry stock should then be sammied, set out, 
oiled off with cod oil. and tacked. On stripping, the hides 
should be seasoned with flaxseed liquor, rolled, and soft- 




m 

Figure 91. — Boarding machine. 

boarded For soft-boarding, the machine shown in figure 91 
is commonly used. 

Vegetable-tanned splits. — The splits taken off untanned 
hides, that is, from hides which are split out of the lime, or 
out of acid pickle, or out of a pickle of aluminum sulphate 
and salt, can be tanned in various ways — with extract of hem- 
lock, quebracho, gambier, and finished into inner-soling and 
other leather. Splits taken from limed hides are drenched 
with lactic acid or some other suitable de-liming material, 
then tacked on sticks and hung in the tan liquor and tanned 
wholly by suspension. Splits taken from hides full of acid 
and salt should be first drummed in a solution of 10 lb. of 
salt and 6 gallons of water for 100 lb. of splits for 20 min- 
utes. This puts all parts of the splits into condition to take 
the tan liquor. The first solution into which the splits are 
placed is a plumping liquor made of hemlock extract, and 
should contain at least 0.6 per cent of lactic acid to swell the 



326 PRACTICAL TANNING 

fibers of the splits so that they will absorb the tannin. The 
splits should then be put into a regular bark yard and worked 
through stronger liquors, being handled every other day, from 
two to three weeks being required to tan them, according to 
their thickness. 

Splits taken from hides pickled with aluminum sulphate 
and salt may be put into weak liquor or drummed therein, 
and then tanned in hemlock liquors of gradually increasing 
strength until they are fully tanned. No salt is needed in the 
liquors, and the sulphate or alum is washed out before the 
tanning is finished. 

The most satisfactory way to tan splits is by suspending 
them in the liquor. Where this cannot be done owing to lack 
of vats, a paddle-wheel may be used, this being better than 
a drum. There is no violent pounding in the paddle, and the 
splits therefore finish up finer than when a drum is used. 
Heavy splits may be put into a 10° bk. quermos extract liquor 
in a paddle until they are struck through. They should then 
be tanned in strong hemlock bark or hemlock extract liquor 
until they are thoroughly filled and tanned. For light, flex- 
ible splits, some softer tannage may be used, such as quermos 
extract, the first liquor being 10°. The splits are then passed 
into stronger liquor, or the weak liquor may be strengthened. 
This method of tanning makes soft splits which require very 
little oil or fat-liquor. 

Before splits which are full of alum, or aluminum sulphate 
and salt are put into extract or bark liquors, it is advisable 
to drum them in weak gambier liquor until they are softened. 
They should then be tanned in strong liquors, the alum and 
salt disappearing before the splits are ready to be finished. 
The splits should never be washed in water before they are 
tanned, or they will be flat and flabby when finished. Splits 
are also improved by being drummed in gambier liquor after 
they are tanned. This has no effect as a tannage, but it does 
improve the texture of the leather. Scouring and cleaning 
the leather is also beneficial ; or the splits after they are fully 
tanned and drained can be rinsed in a vat of water, which will 



STRAP, BAG, AND HARNESS LEATHER 327 

remove any sediment. They should never be put into a drum 
and washed as this causes them to lose their plumpness and 
fall away and become thin. After they are rinsed off, they are 
hung on poles to dry, and when dry, they are dampened and 
stuffed. Rough splits for inner-soling are re-tanned with a 
mixture of two-thirds quebracho extract and one-third hem- 
lock extract, then rinsed and re-tanned with sumac in a vat. 
They are then partly dried and stuffed, a good mixture con- 
sisting of 1 part tallow, 2 parts soap, 6 parts Irish moss, and 
30 parts water. After having been stuffed, the splits are 
set out on a table, and a mixture of 6 parts Irish moss, 1 
part starch and 2 parts soap is rubbed in on both sides with 
a stiff brush. They are then set out with a slicker and hung 
up flat to dry. A jacking completes the work. Tanners who 
want to increase the weight of their splits add a little grape 
sugar to the stuffing mixture. 

Splits taken from hides tanned with hemlock, quebracho 
and chestnut extract in combination process can be worked 
into Goodyear stock by being trimmed after they are split, 
and re-tanned in a paddle with a combination liquor com- 
posed of quebracho and chestnut extract. They may be run 
a short time in a drum with a weak liquor to break up the 
crust caused by the belt-knife. They are then put into a 16° 
liquor and left in it 48 hours, and next placed in piles 48 
hours ; then returned to the liquor for 48 hours, the paddle be- 
ing run about 2 hours in the morning and 2 hours in the after- 
noon. When well filled, they are left in piles for a few hours 
and then put into a drum with the following mixture : For 
50 Goodyears, use 4 lb. of flour, 8 lb. of epsom salts, 1 gal- 
lon of cod oil, 1 gallon of degras, and 10 lb. of talc, all mixed 
together to a smooth paste; then add water at 85° F., to 
make 25 gallons. Run the splits in this solution for a half- 
hour and then put them into piles over night. In the morn- 
ing set them out thoroughly; apply a paste made of Irish 
moss or lissom extract and flour, and hang them up to dry. 
When dry, give them a coat of Irish moss and talc on both 
sides, and roll hard; then dry. 



328 PRACTICAL TANNING 

Softening and stuffing heavy splits. — The dry splits require 
careful dampening and softening. A good way to do this 
is to wet half of them in water; then place a dry split on the 
floor, then a wet split on top of it, then another dry one, 
then another wet one until all are piled-down. Leave them 
there 2 or 3 days to become uniformly soft and damp, keeping 
them well covered. Proper dampening is the secret of soft, 
well-filled goods. The splits can also be dampened by being 
sprinkled with water or sprayed with a hose and left in cov- 
ered piles until they are damp and soft; 200 lb. of dry splits 
should not weigh more than 260 lb. when damp. 

The amount and kind of grease to be used depends upon 
the tannage, and must be decided by the operator. Some 
tannages take more grease than others, gambier and other 
soft tannages not requiring as much as hemlock and combina- 
tion tannages. The harder the grease the more can be put 
in. Sometimes 100 lb. of dry splits will carry over 100 lb. 
of grease, 110 lb. being the maximum. The grease should 
be heated to 125° F., and the drum with live steam to the 
same temperature, before the splits are put in. Some degras 
may be used and a little sod oil, say 10 per cent of it, but 
not more, and this only when the grease is good and hard, 
or when stearine is used in making the stuffing. The splits, 
as well as the grease, having been weighed exactly, should be 
carefully and uniformly dampened, and the right temperature 
maintained during the process. A good stuffing mixture for 
gambier-tanned splits is made of 6 gallons of brown grease, 
4 gallons of common wool grease, and 2 gallons of stearine. 
If the brown grease is good, use less stearine. Use from 4 
to 6 quarts of sod oil to every 12 gallons of the stuffing mix- 
ture. If the splits are very hard, use a half gallon more of 
sod oil to each 12 gallons of stuffing. After having been 
stuffed, the splits are finished by being whitened, blackened 
with soap and lampblack, dried, trimmed, given a paste of 
flour, dried, rolled or glazed and covered with a size made of 
gum tragacanth, lissom extract, dried again, sorted, and 
graded. 



STRAP, BAG, AND HARNESS LEATHER 329 

Stuffing for waxed splits. — To make 100 lb. of stuffing 
grease, take 45 lb. of tallow, 10 lb. of wool grease, 25 lb. of 
stearine, and 20 lb. of paraffin wax. Dissolve the stearine 
and wax, add the tallow and then the wool grease. Use from 
35 to 40 lb. of the stuffing to 100 lb. of dampened splits. Heat 
the drum to 125° F., and the grease to the same temperature. 
Let the drum run 20 minutes with the door closed and 10 
minutes with the door open. Hang the splits up until they 
are well cooled off and stiff; next set them out tightly on the 
back and then on the face side, and hang them up to dry. 

Another formula for stuffing is : Heat hard glucose to 140° 
F. in a suitable kettle. In another kettle place one-half wool 
grease, one-half brown grease, and one-third best stearine, 
and cook thoroughly. Use about 12 lb. of glucose with 40 lb. 
of combination grease, mixing just before using. The glu- 
cose gives good color and weight, but it must be used carefully 
and with judgment. If the splits are too wet or too dry, or 
of hard tannage, no stearine is necessary, good brown grease 
and wool grease and glucose being sufficient under such con- 
ditions. Dampening for stuffing should be done in such a 
manner that 300 lb. of splits take an additional weight of 35 
pounds. 

Harness leather. — Green-salted hides are generally used in 
the manufacture of harness leather. They are washed for 
10 minutes in running water, cut into sides, and soaked for 
48 hours in the pit. When thoroughly soaked they are fleshed 
and limed for 5 days with hydrated lime and sodium sulphide. 
Unhairing is most generally done on the Leidgen machine, 
after which the sides are bated with oropon. When well bated, 
the stock goes to the tail rocker containing an 8° bk. liquor 
with an acidity of 3 per cent. The sides remain in the rockers 
for 8 days, the strength being gradually increased to 15°. 
The liquor in the handlers consists of the mixture of hemlock 
bark, quebracho and chestnut-wood extract in about equal 
proportions. On removal from the head rocker, the sides are 
placed in the first layer for 5 days where they meet a 21° 
liquor made up in the same proportion as the rocker liquor. 



330 PRACTICAL TANNING 

In the second layer the stock remains for 11 days, meeting 
a liquor of 22°. In the third layer, standing 23°, the sides 
remain for 15 days. The spent liquor from the first, second, 
and third layers is used for strong liquor in the head rocker. 
The fourth layer liquor is made up, 50 parts quebracho, 30 
parts chestnut-wood extract, and 20 parts hemlock-bark ex- 
tract, and stands at 20°. Here the stock remains for 25 days. 

To secure more uniform treatment it is customary to use 
dust in the second and third layers. From the fourth layer 
the stock is washed and bleached, wrung out, shaved, and hung 
up to dry. The dry sides are sammied back with water, and 
when properly tempered they are ready for stuffing. 

The stuffing is carried out in a drum with a hot mixture 
of oleostearine, degras, paraffin wax, and tallow, using 38 
per cent on the weight of the stock. The sides, on being re- 
moved from the drum, are hung up to chill and set on the 
grain on a Fitz-Henry machine. They are again set by hand, 
using a dubbin of tallow and cod oil. The well-set sides 
are then hung up and allowed to dry thoroughly. When dry, 
the stock is jacked and snuffed. 

A blacking of hematin and nigrosene is applied to the grain, 
the color being set with an iron striker. Scar paste, which 
consists of a mixture of glue, nigrosene, and potassium ferro- 
cyanide, is then applied. The dry stock is now given a coat 
of tallow and is whitened on the flesh. It is then jacked and 
brushed. 

Good color on heavily stuffed leather. — The moisture 
content of leathers is perhaps the most important point to 
watch in the production of a good color. A leather contain- 
ing too much moisture absorbs the grease with difficulty, but 
leather which is dry absorbs the grease too readily, as already 
mentioned, and allows it to remain on the surface, producing 
a dark color. The fineness of the division of the oil also 
determines the color of the resulting leather. The more finely 
divided the oil the more likelihood there is of producing a 
clear color. It is for this reason that emulsions of oil have 
advantages over pure oils, and since degras produces one of 



STRAP, BAG, AND HARNESS LEATHER 331 

the best emulsions known, it is in great favor with curriers, 
when a light color is desired. 

The nature of the greases which enter into the composition 
of the stuffing mixture is of first importance from the point 
of view of color, it being a good plan to have as large a 
proportion of hard grease as possible, keeping in mind the 
degree of suppleness desired. Solid greases which can only 
be introduced into the leather by the aid of heat, possess the 
property, during cooling, of lightening the color. The use 
of stearine instead of tallow may be of advantage if the 
leather is originally sufficiently soft, since it produces greater 
firmness than tallow. 

In recent years, many solid mineral greases, which possess 
the double advantage of producing good color and of being 
cheap, have been put on the market. Certain of these products 
have the special advantage of being emulsifiable with water, 
thus playing the part of a solid grease in the shape of a fine 
emulsion. It is also possible to mix these materials with tal- 
low or stearine in such a way as to produce greases having 
varying melting points, according to the degree of suppleness 
desired. The solid mineral greases which are emulsifiable gen- 
erally have melting points somewhere about 113° F. They 
may be used alone or in an admixture with tallow. If used 
with the latter, the melting point may go down to 95° F., 
which is helpful for suppleness. These greases may also be 
mixed with stearine, or with a mixture of tallow, stearine, 
and moellon. By this means it is possible to obtain a much 
brighter color than was formerly possible by the old processes 
of currying, a greater quantity of grease being introduced at 
the same time. This is not harmful to the quality of the 
leather, rather beneficial. Goods thus stuffed have, in fact, 
a greater tendency to maintain the dry appearance of well- 
stuffed leather. 

One of the features of the superiority of modern currying, 
as viewed from the final color of the leather, rests in the 
practicability of stuffing the leather in a drum. It will be read- 
ily understood that this treatment possesses the advantage of 



332 PRACTICAL TANNING 

increasing the fineness of the division of the grease, thus al- 
lowing it to penetrate the fibers of the leather and be assimi- 
lated more rapidly, all of which helps in the production of a 
satisfactory color. To this advantage may be added the fact 
that a considerable proportion of hard grease, at least 25 to 
30 per cent of the total, can be used ; and a finished leather 
will be produced, which, in drying, will not make apparent 
the amount of grease which has been incorporated. 

For the drum stuffing of leather there are two common 
methods of procedure : the first being to apply the grease to 
the leather on the table, and when thus plastered, to drum it 
in a heated drum; the second treatment being to warm the 
drum, and after introducing the leather, turn it for a few 
minutes to warm the latter. The grease, at a suitable tem- 
perature, is then put in, and turning is continued from a half 
to one hour, until all the grease has been absorbed. Curriers 
who use the first method give it preference. A leather of 
good color is very easily produced by this process, but it is 
probable that a less quantity of grease is introduced than by 
the second method. If it is not desired to introduce a great 
quantity of grease into the leather then this first method, that 
is, to apply the grease on the table and drum afterwards, may 
be used ; but it is quite probable that just as good a color may 
be obtained by the second method, and at the same time a 
larger proportion of grease be introduced. The chief reason 
why some curriers do not succeed with the second method is 
that they do not sufficiently study, before stuffing the leather, 
its condition as regards moisture, its proper condition in this 
respect being indispensable for success. If the hollow or 
loose parts of the leather are not sufficiently dampened at the 
moment the goods are put into the drum they will absorb 
too much grease, and too dark a color will result, while the 
other portions will remain insufficiently stuffed and will be 
of a much lighter color, a bad result. 

The secret of success in direct drum stuffing rests in putting 
the leather into proper condition of moisture before stuffing; 
this work should be entrusted only to a skilled man, who can 



STRAP, BAG, AND HARNESS LEATHER 333 

detect at a glance the hollow part in the leather and how 
much moisture should be given to it. Once the leather is 
properly dampened, giving more to the hollow parts, it should 
be placed in a pile for a sufficient period for the moisture to be 
evenly distributed among the fibers, and then to proceed to 
the stuffing. With these precautions observed, the second 
method of manipulation will give a color just as good as the 
first, and in addition, it will allow a much larger propor- 
tion of grease to be introduced into the leather. 

As a final precaution, the stuffing formula should contain 
an emulsifying agent, which will ensure a perfect emulsion 
of the whole ; for example, soluble oil, moellon, or one of 
the mineral greases mentioned, which being themselves emulsi- 
fiable, impart this property to the other greases. 

Certain curriers make it a practice to open the door of the 
drum after the absorption of the greases, and continue the 
turning of the drum until the greases solidify. There is, how- 
ever, no marked advantage in this method. It seems prefer- 
able, as soon as the grease has been absorbed, to remove the 
leather and to hang it up until cold. After this, it is good 
practice to soak the goods in a sumac bath for one or two 
days until complete penetration has taken place, and finally 
set them out. In this way, other things being favorable, a 
perfectly satisfactory color will be obtained. 

The stuffing of belting leather can be carried out either on 
the table or by immersion. There is an indispensable precau- 
tion to be taken in order to produce a good color, and that is, 
when stuffing is carried out by hand, to moisten the grain 
lightly in order to prevent the grease from penetrating through 
to it. Without this precaution the grease traverses and makes 
the surface a dark color. On the other hand, moistening the 
grain causes the grease to set the moment it reaches it, and 
thus helps to maintain the color. 

There is also another method of procedure which gives 
good results, and that is, the grease must be appreciably hotter 
than the leather. On a table, which should be a little larger 
than the butts, are placed a certain number of pieces of felt 



334. PRACTICAL TANNING 

capable of absorbing moisture easily. These pieces should be 
as large as the table itself, and on top of them is placed a 
similar piece of felt, the whole forming a soft cushion on the 
table, which is kept wet. Each butt, on coming from the hot 
chamber, is placed grain downwards on the cushion, and the 
grease is applied to it in this position. The cushion, by its 
softness, adapts itself to the surface of the butt, and its mois- 
ture prevents the grease from penetrating to the grain, because 
as soon as the grease traverses the leather and reaches the 
moist grain, it sets. In spite of this, it is essential that the 
grease should be applied as rapidly as possible, as the butt 
must be allowed sufficient time to cool down during the process. 
Finally, great care must be taken that the temperature of the 
grease always remains the same. Immediately after this ap- 
plication of grease the butts are immersed either in cold water, 
in weak liquor, or in a sumac liquor, and left there two or 
three days. This obviates drumming the leather after stuffing, 
an operation which always causes a loss of weight. The 
longer the butts are allowed to lie in this liquor the greater 
the chance of causing the dark stains, which may have been 
produced on the grain, to disappear. The butts are finally 
rinsed in cold water and set out carefully on a table. The 
grain is moistened regularly with water, and a mixture of 
tallow and cod oil in equal parts is applied to it cold, a good 
natural color being thereby produced. If a lighter color is 
desired, less grease is given. There are other precautions 
that may be taken after stuffing, which help to produce a good 
color. In the first place, the drying after stuffing must take 
place very slowly. 

The temperature of drying must not be too high, other- 
wise the grease will melt and appear on the surface. It is, 
however, necessary that the drying should be carried out in 
a sufficiently high temperature for the greases to remain soft, 
in order that they can be finely divided as they penetrate to 
the interior of the leather. The temperature most suitable 
must be determined by the melting point of the grease em- 
ployed. In some works, time is saved by not drying out com- 



STRAP, BAG, AND HARNESS LEATHER 335 

pletely, but by setting out in the half-dry state. It is, how- 
ever, much more preferable to dry completely and dampen 
back again regularly in order to set out. This precaution 
should especially be observed when dealing with leather stuffed 
by dipping. It is good practice after currying to leave the 
goods in the warehouse for a sufficient time for the grease 
to be properly assimilated in the interior of the leather. After 
this period the last trace of grease which remains on the 
grain may be removed with care by means of a fine slicker. 

The process of bleaching, which contributes to the produc- 
tion of a regular and light color, can be carried out after 
tanning, either before or after stuffing. In principle, bleach- 
ing before stuffing is to be preferred. Weak solutions of 
.oxalic acid, sulphuric acid, potassium oxalate, or sulphurous 
acid are used. There are also on the market products called 
"hydrosulphites," either under this name or under special trade- 
marks. These materials enable one to produce an efficient 
bleaching in a simple manner, the solution being prepared 
at time of using. In spite of the superiority of bleaching 
before stuffing, it often happens that it is more convenient to 
bleach after the stuffing. A method of bleaching leather, 
which has been stuffed with a large quantity of grease, is as 
follows : The first precaution is to remove completely all ex- 
cess of grease from the surface of the grain. The butts are 
placed in a pile for 24 hours and immersed for one minute in a 
bath at 77° F. containing 3 per cent of caustic soda, the leather 
thereby becoming very dark. It is washed in tepid water, and 
then placed in a cold 5 per cent solution of hydrochloric acid 
until it becomes light again, when it is carefully rinsed with 
cold water. This process must only be taken as an example. 
In principle, the processes of bleaching used before stuffing 
may be equally well used after stuffing, but to make their 
application successful after stuffing it is essential that every 
trace of grease shall be removed from the grain. This can 
be accomplished by means of a good washing with a soap 
solution, followed by careful rinsing. The ordinary process 
of bleaching can then be applied, and may be combined with 



336 PRACTICAL TANNING 

treatment in sumac. For belting leather, the butts, after hav- 
ing been washed and set out by machine on flesh and grain, 
are placed in a pit, together with a strong lukewarm sumac 
liquor, and left therein one day, being removed two or three 
times. The sumac may also be given in a drum for one or 
two hours. The butts are set out on a table with a stone 
slicker, carefully brushed, allowed to dry gently, and placed 
in a pile when half dry. Treatment in a sumac bath helps 
to brighten the color of harness leather also. The quantity of 
sumac depends upon the nature of the original tannage, but 
about 2 lb. per butt is an average quantity. In the manufac- 
ture of harness leather, and especially for leather that is to be 
stained with light colors, special precautions are sometimes 
taken. In the first place, only hides of particularly good 
color are selected. After shaving, they are drummed in a 
sumac bath, which has already been used once before, then 
set out by machine. They are then given a second sumac 
bath, this time one freshly prepared. The treatment with 
sumac does not necessarily exclude chemical treatment with 
oxalic acid. If the two processes are combined, the color 
obtained is even lighter. If the suggestions given are fol- 
lowed it Is possible to obtain a leather which has absorbed con- 
siderable grease and is of sufficiently light color and dry ap- 
pearance to satisfy the most exacting customer. 

Automobile leather. — For automobile, carriage, and up- 
holstering purposes, spready hides are used, so that the hide 
dealer or tanner taking up the stock makes his selection on 
spreadies. The hides used for this class of leather are usually 
green-salted. 

In the preliminary work the hides are soaked, fleshed, 
limed, unhaired, and bated. They are then run in the paddle 
with an acid-spent tan liquor to set the grain and impart a 
uniform color. The hides, having been colored, are sus- 
pended by the butt in rocker frames, in which case the pits 
must be sufficiently deep to prevent sagging to the bottom. 
The rocker system for this class of stock is worked on the 
same principle as that described under sole leather. 



STRAP, BAG, AND HARNESS LEATHER 



337 



Tanning. — The liquor commonly used in the rockers con- 
sists of a mixture of hemlock and chestnut-oak bark. The 
tail liquor should be very weak, stronger liquor being used 
as the tanning progresses. Usually from 8 to 10 days is 
a sufficient time for the rocker treatment, as it is only nec- 
essary to bring the hides into such a condition that they may 




Figure 92. — Sheridan embossing press. 

be split. The rocker liquor, of course, should be sufficiently 
acid to produce the necessary plumpness. 

On removal from the rockers, the hides are passed through 
the wringer, and are then worked on the stoning- jack to re- 
move any wrinkles and smooth out the leather. A grain split 
is first removed, and the remainder again split into various 
weights according to market demands and the judgment of 
the splitter. The grains split are usually re-tanned in a drum 
with quebracho or a mixture of quebracho and gambier. The 
flesh splits are, as a rule, re-tanned in the paddle, although 
some tanners prefer to re-tan in the pits. For re-tanning the 



338 PRACTICAL TANNING 

flesh splits gambier is very largely used, but sometimes mixed 
tannages are employed. 

The re-tanned splits are next run in a paddle with sumac 
liquor, to which degras in the form of an emulsion is added. 
They are then set out carefully either by hand or machine 
and given a coat of degras and cod oil. Having been oiled, 
the leather is tacked closely on special frames, these being so 




Figure 93. — Embossing machine. 

constructed that the leather may be stretched in all directions, 
clamped in the extended condition, and allowed to dry. 

The dry leather is removed from the frames, broken to 
make it soft, and after buffing is ready for the application of 
the finish. 

Finishing. — The finish of this leather is usually made by 
boiling linseed oil with a drier and some pigment. The oil 
is heated over a coke or oil fire to a temperature of about 
600° F., and is allowed to cool to about 350°. The fire is 
then extinguished, and the necessary amount of naphtha is 
slowly added. This produces a jelly-like mass known as 
"sweetmeats." The pigment, which has previously been 
ground in oil, is now carefully incorporated and forms what 
is known as the "daub." 

The grains and splits, having been assorted for grades, are 
stretched on frames and given a heavy coat of daub. This 
material is applied evenly, and the excess is removed with a 



STRAP, BAG, AND HARNESS LEATHER 339 

slicker. The hide is then allowed to dry in the air. A sec- 
ond coating of the same material is applied; and the frame is 
placed horizontally in the drying oven in which a tempera- 
ture of 120° F. is maintained. The third coat consists of 
plain boiled linseed, which is dried in the oven at a tempera- 
ture of about 130° F. When perfectly dry, the surface is 




Figure 94. — Turner hydraulic embossing and 
smooth-plate press. 

rubbed down with a brick of pumice stone. The number 
of daub coats and varnish coats varies, the brighter the finish 
desired the more varnish applied. After the bottom or daub 
coats the finishing coats are always rubbed down with pumice 
before application of another coat, except in the case of the 
last coat, which is not pumiced. After thorough drying in 
the oven, the frames are placed in the sun to remove the 
stickiness, and after sun-drying the splits are stripped and 
trimmed, and are ready for market. 

The greater part of this kind of leather is embossed in order 
to produce an imitation grain. This grain may be of various 
designs and color according to the demands of the trade. 
Figures 92, 93, and 94 show three kinds of presses used for 
this purpose. 



340 PRACTICAL TANNING 

In place of the daub coat above mentioned, many other 
materials and combinations of materials are used; the most 
common, however, is pyroxylin. 

"Spanish leather," so called, which is much used at present, 
is produced by tanning the hide in strong quebracho liquor 
which draws up the grain and gives the leather its unique 
appearance. In finishing this leather it is dyed to shade and 
then rubbed over with a pigment in oil. The excess of pig- 
ment is removed from the surface by brushing, but leaves a 
color in the wrinkles. The same effect, however, is more 
commonly produced by finishing with linseed oil daub, and 
then embossing the product with a Spanish grain. The color 
in the wrinkles is produced in the same manner as just 
described. 



CHAPTER XII 
PATENT LEATHER 

Patent leather. — Any leather that carries on the surface 
a high-gloss varnish finish is called "patent leather." The terms 
japanned, enameled, and patent are synonymous, except that 
enameled leather is usually that in which the finish is applied to 
the flesh. The following description is taken largely from a 
lecture given by George W. Priest before the tanning and 
applied leather chemistry students at Pratt Institute, Brook- 
lyn, N. Y., for which the author desires to give him full 
credit : 

In a description of patent leather the subject should be 
divided into three parts, namely, (1) raw materials; (2) 
preparation of compositions and varnishes; and (3) applica- 
tion of the above. 

The raw materials used in making patent-leather composi- 
tions and varnishes are : linseed oil, turpentine, naphtha, solu- 
ble cotton, amyl-acetate, lampblack, Chinese blue, Prussian 
blue, umber, litharge, and spirit black. 

Linseed oil. — This material belongs to the class of oils 
which absorb oxygen from the air and dry to an elastic, 
flexible film of varnish. No other oil approaches linseed in its 
drying properties. 

The oil is expressed from flaxseed which comes from Rus- 
sia, India, South America, and the United States and Cana- 
dian Northwest. That made from the North American seed 
makes the strongest and most flexible varnish. Calcutta comes 
next, making a softer varnish, while the South American seed 
is poorest. Consumption of linseed in America is so great 
that the domestic production is too small, and supplies have to 
be drawn from India and Argentina. 

It was formerly believed that Calcutta oil made the best 

341 



342 PRACTICAL TANNING 

varnishes. This idea probably arose from the fact that all 
the Calcutta oil was expressed, made up, and tanked ready for 
use as soon as it came in. This tanking gave the oil an age- 
ing which made it better. The domestic oil was expressed 
and sold at once. An oil kept for a long time at a moderate 
temperature makes a more brilliant and flexible varnish, and 
one which works freer. 

The present great demand for linseed oil does not permit 
of any long storage in refiners' hands, so that oil is put on 
the market only a few weeks old, often only a few days. 
Modern methods of refining have been so perfected that a 
fresh refined oil is better than some of the old tanked oils. 

Two classes of oil are sold to the patent leather manufac- 
turer. One called an "aged" oil, which has received some 
beneficial treatment in the refinery, is used for making the 
"daub" or bottom coats. The treatment causes the oil to 
"body" more quickly so that the cooking time is shortened. 
This oil is of a softer nature than the varnish oils. 

For the varnish coats a refined varnish oil is used, although 
there is no reason why the "aged" oils should not be used. 
Special varnishes and other patent-leather compositions are 
of such a heavy and viscous nature that some solvent must be 
mixed to thin them so that they will flow freely under a brush. 

Turpentine. — This makes an ideal thinner as its boiling 
point is high enough to permit plenty of time in brushing 
before it evaporates. It was formerly used to thin down the 
varnishes so that they would flow easily, but the high price 
has almost prohibited its use, although some tanners still use 
it mixed with naphtha. 

Naphtha. — Two grades of naphtha, motor gasoline and V. 
M. & P. naphtha, are used for reducing varnishes and compo- 
sitions. The former dries out completely in a short time, 
while the latter takes more time and probably never com- 
pletely evaporates. The higher boiling portions of the heavier 
naphthas have been known to cause serious trouble, and at- 
tention must be given to these goods to see that they run 
uniform and dry completely. 



PATENT LEATHER 343 

Soluble or nitrated cotton. — This is the non-explosive form 
of guncotton, which, when reduced with amyl-acetate, is used 
as a lacquer. Mixed with camphor it forms celluloid. Ni- 
trated cotton makes a very tough, transparent film that cannot 
be used alone for producing a finish on leather, but must be 
mixed with some kind of oil. 

For patent leather it is customary to mix the cotton with 
boiled oil and amyl-acetate. Such a composition is particu- 
larly adapted for small fine-grained skins like kid or coltskin. 
Amyl-acetate is the only practical solvent for guncotton, and 
gives the best results on leather. It may however be mixed 
with a small proportion of naphtha without precipitating the 
cotton from solution. 

Lampblack. — In order to get a black foundation for the 
bottom coats a very fine grade of lampblack is used; this 
lampblack weighs about 4 lb. to the barrel. 
..Chinese bine. — This comes in lumps or powder of an iri- 
descent purple color. It is used as a dryer in making var- 
nishes. Some makers use the lumps directly in the kettle ; 
others buy the blue in powdered form ; and still others powder 
the blue, grind it in oil, and then boil it with the varnish. 
Any one of these methods seems to make equally good varnish. 

Prussian 6/we.— This salt, which is of nearly the same chem- 
ical composition as Chinese blue, is used ground in oil, with 
a little black, and mixed with the bottom coats as a pigment 
to give color. 

Umber. — This is used as a dryer in the oil boiled for the 
bottom coats. 

Litharge. — A lead oxide, is sometimes used with umber 
and sometimes replaces it. It makes a softer coating than 
the umber. 

Spirit black. — This is a coal-tar color used to give color to 
the nitrated cotton coats. 

Boiling the oil for the daub coat. — The bottom or daub 
coat acts as a filler or sizing on the leather, whether it be 
chrome or vegetable-tanned. In order to keep this coat from 
penetrating too deeply and so injuring the leather, the oil 



344. PRACTICAL TANNING 

is boiled to a very heavy, viscous mass. This requires a 
long time at a fairly high temperature. To assist and shorten 
the time, the so-called "aged" oils are commonly used, which 
have had some treatment that makes them cook and come 
to a body much quicker than a raw oil. The treatment does 
not in any way injure the strength and elasticity of the 
coatings. 

The oil is boiled slowly at first with \ of 1 per cent of 
umber ; the temperature is then raised gradually until it reaches 
575° F. or thereabouts. This temperature is maintained by 
pulling the kettle on and off the fire. As soon as the tem- 
perature reaches about 350°, light vapors begin to come from 
the oil ; these have a rather fragrant odor, but as the boiling 
continues the vapors become much denser and more pungent. 
As the oil breaks up under the heat, oxidation takes place, and 
large quantities of acrolein are given off, which attacks the 
mucous membrane acutely. To protect the oil boiler, the chim- 
ney in which the boiling is done is well ventilated so that the 
obnoxious and poisonous fumes are carried away. 

During boiling, the oil loses about a fifth of its bulk through 
distillation and the breaking up of the glycerides of the oil. 

In Germany, where the phenomena of oil boiling have been 
carefully studied, it has been found that the linolein, which 
is formed by oxidation at low temperatures, is more elastic 
and tougher than the linoxyn formed at higher temperatures. 
When the oil has reached the desired consistence, which 
can only be judged by practice, the kettle is taken off the fire 
and taken about 20 feet away. The outside of the kettle is 
sprayed with water to put out all sparks, and the hose is 
turned on the fire in the boiling-house until the fire is com- 
pletely extinguished. 

The daub is so heavy that naphtha or other solvents will 
not mix with it in the cold, therefore the naphtha is put into 
the hot daub. This sudden addition of cold naphtha to very 
hot daub at once vaporizes the naphtha, which travels along 
the ground like a white fog. For 50 gallons of daub, 100 
gallons of naphtha are generally used, about half of which 



PATENT LEATHER 345 

evaporates. As the lighter parts evaporate first, the heavier 
parts, which are slow drying, are left in the oil. 

A machine patented by George Priest is in use in several 
plants, and by it the daub is stirred mechanically during the 
mixing and the naphtha is caught in a condensing dome. 
No naphtha is lost in this machine, so there are no fumes and 
no danger to the boilers. The daub made by this machine is 
said to be much smoother than by the old method. The 
machines have been in operation for over 15 years without 
explosion or trouble and seem to be practical. 

After the naphtha has been added, the daub is stored ready 
for mixing, which is done by the addition of more naphtha 
and lampblack according to the judgment of the head mixer. 

The consistence of the boilings varies from a heavy body, 
which will string out in silks, to one that is like heavy flour 
paste in body. The more open the leather to be coated the 
heavier should be the boilings. The second coat was formerly 
put on with a slicker, and was the same as the daub, but with 
more naphtha in it. It is now customary to make a special 
boiling, which, when reduced with naphtha, is thin enough 
to be applied with a brush. This color coat contains Prus- 
sian blue in oil. 

Varnish. — As the varnish has to stand all the wear and 
tear of hard usage and weather, the greatest care is taken in 
selecting the oil, and in its cooking. 

The driers used are Chinese blue lumps, about 3 per cent 
on the weight of oil. These are introduced when the oil is 
at about 350° F. In making varnishes, the temperatures are 
raised gradually and with constant stirring. Within reason, 
the lower the temperatures and the longer the time of cook- 
ing the stronger and more flexible is the varnish. Chemical 
changes take place at low temperatures which improve the 
oil, causing the varnishes to become more elastic and to dry 
quicker. The consistence of the varnishes varies with the kind 
and quality of the leather, and is controlled by the boiler. 
The varnish is usually stored 10 days before using; longer 
storage does not improve it enough to warrant extra time. 



346 PRACTICAL TANNING 

Application of compositions to leather. — After the leather 
has come from the de-greasers, it is stretched tightly in frames 
by means of metal toggles. 

The consistence of the bottom coat is largely a matter 
of judgment. The stock daub which contains naphtha, heavy 
boiled sweetmeats, and lampblack, is reduced with the proper 
amount of naphtha in a mixing machine. This is spread 
evenly over the surface of the hide and well rubbed in by 
hand; afterwards the excess is spread off with a steel instru- 
ment called a "slicker." When properly applied, the surface 
should be uniformly black, free from streaks, and should 
stick slightly to the hand. The hide is then stood up to dry 
in a drying room at a low temperature. This coat is not 
exposed to the sunlight. If pyroxylin is used, it is reduced 
with amyl-acetate to give the best results, and applied with 
a sponge and dried in a way similar to the oil finish. 

The second coat is applied on top of the daub on the fol- 
lowing day. The hide receives a slight rubbing with pumice, 
and the second coat is applied with a brush. This composi- 
tion contains some pigment to give color to the leather. It 
is well brushed in, and the hide is stood up in a drying room 
at a moderate temperature. If the hide is very open a third 
coat may be applied. 

Before the varnish is put on, the hide is well stoned and 
carefully brushed with a wet brush to free it from all dust 
which may have been made by the rubbing down with the 
pumice. Great care is taken while varnishing. The room 
is well heated so that the varnish will flow freely. While 
a certain amount of ventilation is necessary, this is so ar- 
ranged that no direct draught blows over the leather under 
treatment. The men work stripped from the waist up to 
avoid flying dust and lint from clothing. The varnish is 
in 15-gallon cans, this size giving the best results because it 
is so deep that any dirt getting in the cans settles at once to 
the bottom far away from the reach of the varnish brush. On 
hides, the varnish is usually applied with a large round brush 
4 inches in diameter and with bristles 8 inches long. A brush 



PATENT LEATHER 347 

full is applied to the hide, and is flowed on and well brushed 
down to avoid streaks and ensure an even coating. The hide 
is then placed in a horizontal position in the oven, the dis- 
tance between the hides being about 3 inches. The tempera- 
ture is gradually raised to about 160° F., and the hide is left 
in over night. The next morning the varnished surface 
should be brilliant, free from dirt, and a bit tacky or soft. 
To overcome this, the hide is generally exposed to the sun- 
light all day. The combination of the ultra-violet rays in the 
sunlight, and the air, finish the oxidation of the varnish, so 
that it is soft and flexible, but will not stick if two varnished 
hides are laid away face to face. 

A method of drying patent leather by the use of the Cooper- 
Hewitt mercury-arc quartz lamp has been developed by George 
Priest. This method has been used successfully in a number 
of plants. The theory is as follows: 

It has been known for a long time that the ultra-violet 
or short wave-length rays in the sunlight produce certain 
chemical results. They bleach linen, discolor dyed leather and 
fabrics, and oxidize oils and varnishes. 

It has also been known that the old form, of Cooper- 
Hewitt lamp produced small quantities of ultra-violet light. 
This lamp is a long tube of glass suspended horizontally from 
the ceiling, which produces a peculiar and somewhat ghastly 
green light, but which is, of all artificial lights, least trying 
to the eyes, and is used wherever much night work is done 
requiring constant application of the eye. 

It is known that the stronger the electric current the more 
ultra-violet light can be produced, but two things prevent 
the common mercury lamp from giving this result ; first, ultra- 
violet rays will not go through ordinary glass (the other 
rays go through, but it acts as a screen for the violet rays) ; 
second, in increasing the strength of the electric current the 
glass tubes were melted. 

Within the last few years the art of making transparent 
quartz has been perfected. Quartz transmits the ultra-violet 
rays, and has such a high melting point that strong electric 



348 PRACTICAL TANNING 

currents, which produce light rich in ultra-violet rays, can be 
used. The lamp was at first found to be very fragile and 
short-lived, but was eventually perfected for patent-leather 
work, and made practical the indestructible quartz lamp of 
today. An exposure of 2 to 4 hours under the quartz lamp 
will accomplish as much as a 6-hour exposure to sunlight. 

The advantage of this method of treating leather is that 
no new materials are used. No change is made in manu- 
facture except in the exposure. Wearing tests in shoes, and 
in leather laid away in piles face to face, has demonstrated 
that there is no difference between sun-treated and lamp- 
treated leather. 

This method eliminates factory shut-downs during pro- 
longed periods of wet weather, or in extra exposures during 
the hot, humid days of summer when varnishes dry poorly. 

After the leather has been exposed to sunlight or ultra- 
violet rays, it is stood up in a cool place over night and the 
next day cut from the frames, trimmed, and piled away face 
to face for a few days, when it is ready for shipment. 

While at present more is understood about the manufac- 
ture of patent-leather varnishes and compositions, much more 
technical skill is required than formerly on account of the 
varying qualities.of linseed oils, and the type of naphthas now 
supplied, which are not always adapted to the requirements 
of the patent-leather manufacturer. Close chemical checks 
should be kept on the oils and solvents used. The oil and 
naphtha agents should not be blamed, however, because they 
can only sell what comes to them, but, recognizing what is 
coming, proper treatment can be given the article in question. 
This can only be determined by chemical test. 

The real problem, however, which confronts a tanner of 
upper leather, is to make a leather that stands the mechani- 
cal treatment of the shoemaker. It almost seems as if the 
wearing of the shoes was a secondary consideration. Prob- 
ably the shoeman takes it for granted that all leather will 
give good satisfaction in shoes. 

Leather must stand the heavy pull of the lasting machine 



PATENT LEATHER 349 

and other devices for making the vamp fit the last snugly. 
The leather is almost invariably wet before lasting, the tip 
is not only wet but also stuck to the lining with alcoholic 
shellac cement; frequently the vamp is soaked in sulphonated 
oil "to help it," and is often given some secret mixture which 
the foreman of the lasting room has found effective. In a 
few places the leather is lasted without treatment. 

Attention is called to this treatment previous to lasting, 
because the patent leather tanner must always have it in 
mind. All leather is more stretchy when wet or damp than 
when dry, and all damped or wetted leather contracts on 
drying, and if stretched too tight when wet and held firmly 
in place will frequently crack on the grain. 

Leather is generally carefully cut into vamps, the cuttings 
being selected for the proper parts of the shoe. 

The vamps are next stitched to the uppers and then damp- 
ened, lightly tacked on the last, put into the pulling-over 
machine, and under heavy pressure made to fit the last snugly, 
and then tacked. They are left in this condition over night 
and the next day the soles are stitched on, which operation 
tightens the vamp still more. A pressure of probably 75 lb. 
to the square inch is applied and held there. There is no 
give to this pressure as long as the last stays in the shoe. 

Today the shoemaker demands a piece of leather which is 
more or less firm. Such leather makes a good-looking shoe 
because it "stands up in the shoe," as they say; in other 
words, the shoe retains its shape and looks well on the counter. 
It also wears well and the shoe does not slump over and lose 
its shape. But the tanning and currying methods which make 
such a leather also tend to make a weak grain, and a leather, 
which, when wet, is a bit rubbery, so that on drying there 
is considerable contraction and a consequent parting of the 
grain. 

The manufacture of patent leather is then a mechanical 
problem. Glazed kid, box calf, colored calf, and velour 
leathers all have oil in them, and have never been subjected to 
any drastic treatment or high temperatures. They are fre- 



350 PRACTICAL TANNING 

quently oiled off before being shipped to the shoe factory. 
In cutting the vamps from such leathers the greatest care is 
used to get the right selection for the vamps so as to make 
a good-looking shoe. The exact reverse of this treatment is 
given patent leather. 

Most patent leather is tanned almost to the limit of crack- 
ing in order to get the stretch out of the leather. A minimum 
amount of oil is given it in the fat-liquor, and this is after- 
wards washed out with a naphtha bath. The leather has 3 or 
4 coats of linseed-oil compositions and 3 or 4 days tempera- 
ture of 110 to 160° F. The character of linseed-oil varnishes 
is that they are very flexible but only temporarily elastic; 
that is, they will stretch back and forth about 20 per cent; 
but if stretched 20 per cent and held, the film parts at once 
in a long striation. In cutting patent leather, as it all looks 
good and is all expensive, no selection is made in cutting 
vamps and "everything goes," so to speak — and does go liter- 
ally, for bellies, legs, and necks always give trouble. 

This characteristic of linseed-varnish film complicates mat- 
ters. If leather that has received too drastic a treatment in 
the tannery, or for other reasons has contracted when dried 
more than it should, is used for vamps, and is soaked and 
pulled while wet over a last, the varnish, being temporarily 
elastic, will stretch with the grain. But as the leather again 
dries and tightens, the varnish, if it has been put on too heavy, 
is likely to break in long striations. If, on the other hand, 
the varnish has been applied lightly, the grain may break. A 
linseed varnish is slightly hygroscopic and is tougher when 
wet than dry. When patent leather acts as described the re- 
sult is the discarding of shoes made from it. 

In spite of all difficulties, tanning has reached such perfec- 
tion that most leather stands all the shoe factory roughness 
and makes good shoes. 

The strain on the leather during lasting is greatest over 
tips and across the ball of the foot. Cracks on the tip can 
be buffed off, and a heavy varnish, made especially for the 
purpose, put on. This is called "flowing the tips." When 



PATENT LEATHER - 351 

cracks appear on the ball of the shoe on the inside, the vamp 
has to be torn off and another put on. / 

Take at random three patent leathers made by as many 
different tanners : One of these leathers is made with soft 
river water, another with artesian well water, the third with 
lake water. They are all standard leathers, and the success 
of each one seems to show that the kind of water used has 
nothing to do with the quality of the leather produced. This 
means that the tanner has made the best of his local condi- 
tions and adapted his methods to meet them. 

It is interesting to note that each one of these tanners uses 
a different beam-house method. One uses straight sulphide, 
10 per cent in a paddle-wheel ; another 5 per cent lime and 
5 per cent sulphide; while a third uses 6 per cent lime and 1 
per cent sulphide. They all use different bates. 

Two of these people de-grease their leather, and one does 
not. Two tack their leather out on frames in the tannery, 
and the other one has the leather stretched in the japanning 
frames, but does not tack in the tannery. The point is that 
adaptation of proper methods to the local tannery always pro- 
duces good leather. The methods must be practical of course. 
Because one man makes good leather with sulphonated oil 
it does not mean that he could not do the same with soap and 
oil. If the reason were traced back why his leather seemed 
to be better adapted to a sulphonated oil it might lead to the 
beam-house. And it might be found that it were better to 
operate the beam-house as it was, rather than change the fat- 
liquor. The making of a successful leather is the blending 
of methods and materials which give best results for the local 
plant. 

In the manufacture of patent leather, many tanners take 
advantage of the fact that hides and skins with poor grain 
can be successfully put into such leather, which is done by 
tanning in the usual manner and then snuffing off the grain. 
In fact, even high-grade side leather is often snuffed in order 
to make the finish adhere more closely. 



CHAPTER XIII 

DYEING LEATHER 

Having carried out the various processes of soaking, de- 
pilating, bating, and tanning for glove, fancy, shoe, and other 
pliable leathers, the next step to be considered is the method 
employed in coloring the product to meet the demands of the 
trade. A short description of the various classes of dyes will 
be given, together with a general outline of their application, 
and an effort made to point out what conditions are best 
suited for the different grades. 

Classification of dyestuffs. — The earliest classification of 
dyestuffs divided them into two classes, "substantive" and 
"adjective." Substantive colors are those which are capable 
of producing a fully developed color upon textile material 
without the assistance of any other combining substance; ad- 
jective dyes are those which require an intermediate combin- 
ing substance, called a "mordant," to fix and fully develop the 
color. This grouping is still in use, but during recent years 
the tendency has been to use the term "direct" color in place 
of substantive, and mordant color in place of adjective. In 
general, this classification holds good, but there are certain 
grades of color that are direct on some fibers, but require 
a mordant on others. 

A classification which divides the dyestuffs according to 
their origin is of broader application. It recognizes three 
groups as follows: (1) natural organic dyestuffs; (2) min- 
eral dyestuffs; and (3) artificial organic dyestuffs. 

Though the various subdivisions of this classification, par- 
ticularly of the artificial organic dyestuffs, are numerous, this 
classification has the advantage that one class does not overlap 
another. 

Natural organic dyestuffs. — A subdivision of natural or- 
ganic dyestuffs is as follows : ( 1 ) indigo and related com- 

352 



DYEING LEATHER - 353 

pounds; (2) logwood; (3) dyestuffs producing shades of a 
red character; and (4) dyestuffs producing shades of a yel- 
low character. 

Indigo.— Indigo blue or indigotin is found in many plants, 
but the natural product has been almost completely replaced 
by the synthetic material. As it has practically no use in the 
dyeing of leather it is of no particular interest to discuss it 

in this volume. . 

Logwood.— This is the product of a large tree known as 
haemotoxylin campechianum. The wood is rasped or chipped 
and extracted with water, and this solution is evaporated 
either to a syrupy consistence or powder, and is sold as liquid 
or solid extract. If evaporation be done in an atmosphere 
free from oxygen, the product is known as unoxidized log- 
wood extract, and contains haematoxylin as its active princi- 
ple. If, however, air is blown through the solution, a change 
takes place and the product is then known as oxidized log- 
wood extract or hematin, and contains haematein as its 
active principle. 

Logwood is a mordant dyestuff requiring a metallic mor- 
dant to fix it on the fiber. This mordant in the leather in- 
dustry is usually spoken of as a striker. The mordants used 
with logwood in dyeing leather consist of salts of iron, chro- 
mium, copper, nickel, antimony, and titanium. This dyestuff 
is used in producing black or other dark shades. 

Brazil zvood, peach wood, and Japan wood. — Extracts from 
these woods are sometimes used in dyeing leather, but require 
a mordant to develop the color. The metallic mordants used 
are salts of aluminum, antimony, tin, and titanium. 

Fustic, or Cuba wood, contains a yellow dyestuff obtained 
from the wood by leaching. It comes to the tanner as a 
liquid or solid extract and may be used either with an alumi- 
num, chromium, iron, titanium, or antimony mordant. 

Osage orange.— The wood of the osage orange contains 
a bright yellow dyestuff which has largely replaced fustic in 
the dyeing of leather. 

Cutch.— This material is used to some extent in producing 



354- PRACTICAL TANNING 

brown shades when mordanted with copper. Its application 
however, is very limited in the dyeing of leather. 

Mineral dyestuffs. — As a class, these substances are very 
unimportant so far as their application to leather is concerned. 
As a color, however, for certain classes of leather finish they 
are fairly largely employed. In recent years the use of pig- 
ments with some form of binder has come into fairly wide- 
spread use, and they are not only being employed in finishes, 
but find application in the actual coloring of the stock. 

Artificial organic dyestuffs. — The dyestuffs belonging to 
this group are legion and may be classified according to their 
derivation, their composition, or in respect to the character- 
istic, color-forming groups they may contain. As these class- 
ifications are of no particular interest to the leather colorer, 
and as many groups of color have no value when used on 
animal fiber, we will simply consider such groups as are ap- 
plied in the dying of leather, which are as follows: (1) 
basic colors; (2) acid colors; (3) direct colors; (4) aliza- 
rine colors; and (5) developed colors. 

Basic colors. — Chemically the basic dyestuffs belong to that 
class of compounds known as substituted ammonias or amines. 
Like ammonia, they are basic in character, hence the name. 
Basic colors have a direct affinity for vegetable-tanned leather, 
while with chrome-tanned and other leathers they must be 
first mordanted with tannic acid before the basic color is 
applied. Basic colors are characterized by their great bril- 
liancy and high coloring power. They are, however, not very 
fast to light and do not penetrate the fiber. 

Acid colors. — These colors are called so on account of their 
acid character. From a chemical point of view they may 
be divided into three classes : ( 1 ) those which are nitro 
compounds; (2) those made by treating basic colors with 
concentrated sulphuric acid, thereby introducing the sulphonic 
acid (HSO3) group; and (3) those which contain the azo 
( — N=N — ) group. 

Acid dyes are applied direct to leather without any mor- 
dant. It is customary, however, to give the stock a bottom 



DYEING LEATHER - 355 

of some vegetable coloring material in order to secure full- 
ness of shade. The color is applied in an alkaline solution 
and is finally fixed by the addition of a small quantity of 
acetic, formic, or lactic acid. Acid colors are very fast to 
light and penetrate deeply into the fiber. They are not, how- 
ever, as brilliant as basic colors. 

Direct colors. — These colors have a direct affinity for cot- 
ton and so get the name. Their method of application to 
leather is the same as for acid colors, and like them are also 
fast to light and readily penetrate the fiber. 

Alizarine colors. — These are derived from anthraquinone, 
and are usually applied to leather in the presence of sodium 
dichromate. They are made more soluble by the addition of 
borax and are fixed upon the fiber by means of an acid. Aliz- 
arine colors, like acid and direct colors, are very fast to light 
and penetrate deeply into the leather. 

Developed colors. — Such colors as are fixed on the fiber 
by means of some developing agent are used only to a lim- 
ited extent, but when once produced give very full shades and 
are fast to the light. 

Dissolving dyestuffs. — Natural dyes may be dissolved in 
boiling water. 

Basic dyes are best dissolved in distilled water or rain 
water. Where only well or river water is available — either 
of which is more or less hard — the addition of acetic acid is 
recommended. The basic dyestuff is first made into a thin 
paste with a little cold water and the requisite amount of 
acetic acid (generally one-half the amount of acetic acid, 28 
per cent, as of dyestuff used is sufficient). This paste is 
then poured into the necessary amount of hot water ( 180 
to 190° F.) and stirred until completely dissolved. Actual 
boiling with live steam should be avoided. 

Acid dyes are best dissolved by boiling with the requisite 
amount of water. No acid should be added while dissolving 
the color or to the stock solution. 
Never mix an acid with a basic dye. 



356 PRACTICAL TANNING 

Preparatory treatment before dyeing vegetable-tanned 
skins. — In order to obtain satisfactory results it is necessary 
to prepare the skins properly before dyeing. They are thor- 
oughly soaked and washed in lukewarm water to remove all 
excess of tannin which might cause difficulty during the dye- 
ing operation. If the tannage is dark it is advisable to give 
a slight re-tannage after the washing, with light-colored tan- 
nins like sumac. This is given in the drum or paddle-wheel 
and usually requires half an hour. After the tannin has been 
taken up by the leather it is advisable to fix it with tartar 
emetic or titanium-potassium oxalate (^ to 1 oz. per dozen 
skins). These salts are dissolved in water and added to the 
drum or paddle-wheel after the re-tannage, running the skins 
10 to 15 minutes longer. The skins are then rinsed and are 
ready for dyeing. 

Dyeing vegetable-tanned leather. — There are four 
principal methods of dyeing, namely, brush, tray, drum, and 
paddle dyeing. 

Brush dyeing. -r-This is used mostly for large leather, that 
is, heavy cowhides used in bags, harness, and upholstery; also 
for light leather in cases where an unstained flesh side is de- 
sired. A dyestuff solution of proper strength is applied to 
the dry leather with a medium hard bristle brush. Accord- 
ing to the desired depth of shade one or more coats of the 
brushing solution are applied. The leather is then hung up 
to dry. 

Tray dyeing. — This method is used on light skins only 
where an unstained or only slightly stained flesh side is de- 
sired. The moist skins are either folded singly, (lengthwise), 
or. paired together flesh-to-flesh, and dipped for 5 or 10 min- 
utes in the warm dyestuff solution in the tray until the de- 
sired depth of shade is obtained. Then the leather is hung 
up to dry. Owing to the great amount of labor required for 
so small an output, this method is not largely employed. 

Drum dyeing. — This is the method most generally used. 
Light side leather, kips, horsehide, calf, sheep, and goatskins 
are all dyed in this manner. The drum is loaded with the 



DYEING LEATHER 



357 



leather and sufficient warm water to allow easy moving of 
the leather while the drum is running. The temperature of 
the bath is 100° F. Then the drum is started, and the dye- 
stuff solution is added through the gudgeon while the drum 
is running. Dyeing requires from 30 to 45 minutes. Other 
ingredients or chemicals such as acids, metallic salts, etc., 




Figure 95. — Coloring goatskins. 

which may be required for the proper development of the 
dyeing, are also added in the same manner. 

Paddle dyeing. — This is mostly used for the dyeing of 
very light leathers, such as skivers or light sheepskins which 
might be torn by the violent pounding in the drum. The 
paddle-wheel is filled with water at 100° F., the wheel is set 
in motion, and the damp skins are thrown in. The dyestuff 
solution is then added in portions by pouring it slowly out of a 
dipper and alongside the wall of the paddle-wheel. Dyeing 
requires about a half-hour. Should other chemicals (acid or 
mineral salts) be needed during the dyeing process they should 
be added in solution while the paddle-wheel is running. Basic 



358 PRACTICAL TANNING 

dyes are dyed without additional chemicals. Acid dyes re- 
quire the addition of about half the amount of acetic acid as 
of dyestuff used, or quarter the amount of sulphuric acid. 

When the dyeing process is completed, the skins are rinsed 
in water, set out, oiled off, if necessary, and dried on frames 
or on hooks. 

Dyeing chrome-tanned leathers. — These leathers are 
dyed in the drum. The treatment preparatory to dyeing is 
as follows : 

After shaving, the weight of the leather is determined. 
This weight serves as the basis for calculating the amount of 
dyestuffs and chemicals to be used in the dyeing process. The 
leather is placed in a drum (figure 95), and washed for a 
half-hour in running cold water; following this it is drained 
and neutralized. Borax, sodium bicarbonate, wyandotte soda 
or similar mild alkalies are used for the latter process. Ac- 
cording to the acidity of the .chrome tannage, 1 to 2 lb. of 
such alkalies will usually ;be found sufficient for 100 lb. of 
leather. Neutralizing is done in the drum at a temperature 
of 90° F., and requires 30 minutes. An excess of alkali 
should be avoided. The leather should be almost neutral 
to litmus paper, or show only' a faint acid reaction. After 
neutralizing, the leather is again washed in lukewarm water 
and is then ready for bottoming. Bottoming is done with 
vegetable products, and serves the double purpose of filling 
the chrome leather and giving a suitable foundation for the 
dyestuff to be subsequently applied, especially for basic dyes. 
The products used belong either to the class of tannins, such 
as osage orange, sumac, gambier, cutch, quermos, etc. : or to 
the vegetable dyestuffs, such as fustic, quercitrone, hypernic, 
or logwood. From 1 to 3 lb. of extracts per 100 lb. is gen- 
erally sufficient. Too much vegetable matter should be 
avoided, as this is liable to change the character of the chrome 
tannage. Bottoming is done in the drum at from 90 to 100° 
F., and requires about 30 minutes. After this period, the 
vegetable extracts are fixed by the addition of a suitable 
amount of mineral salts, such as tartar emetic, titanium-potas- 



DYEING LEATHER 359 

sium oxalate, potassium or sodium dichromate, or similar 
products; the drum is then run an additional 15 minutes. Two 
to four ounces of these salts is sufficient for 100 lb. of 
leather. The leather is then washed in the drum with luke- 
warm water for 10 to 15 minutes, when it is ready for the 
dyeing proper. 

Both basic and acid dyes are suitable for dyeing this class 
of leather. The 'dyeing is done in the drum at a temperature 
of 125° F., and requires about 30 minutes. The drum is 
loaded with the leather to be dyed and with sufficient warm 
water to allow an easy floating of the skins. Then it is 
started, and the dissolved dyestuff is added in two or three 
portions through the gudgeon while the drum is in motion. 
Basic dyes are used without the addition of any acid. Acid 
dyes sometimes require the addition of a little acetic or sul- 
phuric acid to develop their full strength, 4 oz. of the former 
or 2 oz. of the latter for 100 lb. of leather is generally suf- 
ficient to ensure good exhaustion and full development of a 
shade. Where acid is used, it is given at the end of the dye- 
ing operation to allow the color to be taken up uniformly be- 
fore being fixed. 

Blacks on chrome leather. — These are usually dyed on a 
logwood bottom. The leather is first bottomed in the drum 
at 125° F., with from 1 to If lb. of logwood extract or crys- 
tals and with a small amount of soda ash (about 2 oz.) for 
100 lb. of leather. After running 30 minutes, 4 oz. of cop- 
peras or equivalent amounts of other suitable strikers are 
added, and the running continued for 15 minutes. The 
leather is then dyed either in the same or in a new bath (the 
temperature of which is 125° F.) for one-half hour with the 
necessary amount of National nigrosine or National Erie 
black ; then rinsed, fat-liquored, and finished in the usual way. 

Dyes for chrome-tanned calfskins. — The following formulas 
are included by the courtesy of the National Aniline & Chem- 
ical Co., they being for dyes used to produce fashionable 
shades on chrome-tanned calfskins, and are calculated for 
100 lb., shaved weight: 



360 



PRACTICAL TANNING 



Gold Brown 

Bottom 

3 lb. sumac extract paste 
\y 2 lb. cutch 

2J4 oz. titanium-potassium oxalate 

Dye 
12 oz. National resorcine brown R 
954 oz. National wool orange A cone 
\ l / 2 oz. National induline NT 
1J4 oz. National wool scarlet BR 

4 oz. sulphuric acid 

Moccasin 

Bottom 

3 lb. sumac extract paste 
\y 2 lb. cutch 

2% oz. titanium-potassium oxalate 

Dye 

18 oz. National resorcine brown R 
18 oz. National azo yellow A 5 W 
3?4 oz. National induline NT 
6 oz. National fast red S cone. 

4 oz. Sulphuric acid 

Cauldron 

Bottom 
3 lb. sumac extract paste 
W2 lb. cutch 
2J4 °z. titanium-potassium oxalate 

Dye 
12 oz. National resorcine brown R 
12 oz. National fast red S. cone. 

2J4 oz. National induline NT 

3 oz. sulphuric acid 

Chestnut 

Bottom 

3 lb. sumac extract paste 
\y 2 lb. cutch 

2% oz. titanium-potassium oxalate 

Dye 

12^4 oz. National resorcine brown RN 
12 oz. National azo Bordeaux 
354 oz. National induline NT 

4 oz. sulphuric acid 

Morocco 

Bottom 
3 lb. sumac extract paste 
\y 2 lb. hypernic paste 
\y 2 oz. potassium bichromate 
Dye 
12 oz. National resorcine brown RN 
\6 z / 2 oz. National fast red S cone. 
3U oz. National induline NT 

2 oz. sulphuric acid 

Jonquil 

Bottom 

3 lb sumac extract paste 
3 oz. tartar emetic 

Dye in fat-liquor 
T l / 2 oz. National metanil yellow 19S5 
3 oz. National resorcine brown R 
2 oz. sulphuric acid 



Aluminum 

Bottom 
3 lb. sumac extract paste 
1 y 2 oz. logwood crystals 
\y 2 oz. copperas 

Dye in fat-liquor 
2Vi oz. National resorcine brown R 

f s oz. National metanil yellow 1955 
2 oz. titanium-potassium oxalate 

Smoke 

Bottom 
3 lb. sumac extract paste 
1 y 2 oz. logwood crystals 
\y 2 oz. copperas 

Dye in fat-liquor 
\y 2 oz. National nigrosine 27722 
1 oz. National metanil yellow 1955 

Black 

Bottom 

1 lb. logwood crystals 

2 oz. bicarbonate of soda 

2 oz. copperas 

Dye 
1 lb. National nigrosine 128 

Chippendale 

Bottom 

3 lb. sumac extract paste 
\y 2 lb. cutch 

1 y 2 oz. titanium-potassium oxalate 

8 oz. National resorcine brown R 

2 oz. sulphuric acid. 

Top with 
11 oz. National Bismarck brown 53 
y oz. National Victoria green WB crys. 

1 oz. National safranine A 

Gold Brown 

Bottom 

2 lb. sumac extract paste 

1 lb. cutch 

\y 2 oz. titanium-potassium oxalate 
8. oz. National resorcine brown R 

2 oz. sulphuric acid. 

Top with 

9 oz. National chrysoidine Y extra 
y 2 oz. National auramine O 

1 y 2 oz. potassium-bichromate 

Morocco 

Bottom 

3 lb. sumac extract paste 
1 y 2 lbs. hypernic paste 

1 y 2 oz. Potassium bichromate 
iy 2 oz. National fast red. S cone. 
2y 2 oz. National buffalo black NBR 

2 oz. sulphuric acid 

Top with 
^y 2 oz. National safranine A 
7V& oz. National Bismarck brown 53 
y% oz. National methyl violet 2 B 

cone. crys. 



DYEING LEATHER 361 

Coloring alum-tanned leather. — This leather is, as a rule, 
dyed with wood colors which may be shaded with acid dyes; 
another way is to bottom with wood colors and then top with 
basic dyes. The wood dyes are the most durable, but the 
coal-tar dyes are the easiest applied. A mordant is not neces- 
sary, as the alum itself acts as a mordant, and the color ad- 
heres readily to the alum-tanned fibers. Wood-color extracts 
in crystal form dissolve readily in boiling water and give clean 
shades of color on alum-tanned skins. It is necessary to wash 
the skins thoroughly before coloring them. This is done by 
running in a drum, giving three changes of warm water (85° 
F.) and adding a small quantity of ammonium carbonate to 
the second water, say 2 per cent on the weight of the skins. 
Washing consumes about an hour. Some skins require more 
washing than others. A polygonal drum is useful in washing 
and coloring any kind of leather. When a white flesh and 
colored grain are desired, the dye is applied to the grain side 
only by means of a brush or a sponge. Coloring in a drum 
dyes both the flesh and grain side. 

Coloring is carried out best in a drum heated by steam. 
Anthracene yellows and chromate browns are used in the fol- 
lowing manner : The leather is thrown into the drum, and the 
solution of dyestuff at 120° F. and containing 1 per cent of 
ammonia, is poured in and the drum run for 15 minutes. A 
solution of formic acid, well diluted, and in which potassium 
dichromate is dissolved, is then added to the liquor in the 
drum. The temperature is raised by steam to 160° F., and the 
goods drummed at this temperature for 15 minutes. The 
liquor is allowed to cool to 120° F., when 5 per cent of gam- 
bier is added, which is absorbed by the leather in another 
half-hour's drumming. Finally the skins are rinsed in warm 
water, set out, dried, and dressed in the customary manner. 

The anthracene yellows and anthracene chromate browns 
can be combined with each other to produce any desired 
shade. Yellow glove and mitten leather is obtained by color- 
ing with gambier, picric acid, and fustic. Boil 25 lb. of gam- 
bier in a barrel three parts full of water. To this solution 



362 PRACTICAL TANNING 

add 1 pint of muriate of tin and 3 oz. of tin crystals, and 
fill the barrel with water. To color 100 skins use from 6 to 10 
gallons of this gambier liquor in 4 gallons of water at 90° F. , 
and drum the leather for a half -hour. 

Prepare a solution of picric acid and fustic by dissolving 
8 oz. of each in 2 gallons of boiling water, to which add 
1 gallon of cold water. Pour this solution into the drum 
with the gambier liquor, and drum the leather 30 minutes. 
This process of coloring may be applied either before or after 
fat-liquoring. Staking, drumming with powdered soapstone, 
and staking again, completes the process of manufacture, and 
the leather is ready for use. 

Methods of coloring chrome-tanned sheepskins. — The 
coloring of chrome-tanned sheepskins is accomplished in vari- 
ous ways. Artificial dyes are in general use. Drum color- 
ing is usually given the preference over the paddle-wheel, tray 
and brush coloring, as it accomplishes uniform dyeing of a 
large number of skins in a short time and with little labor. 
Skins which are to be colored should be prepared with partic- 
ular care. Only sound skins are suitable and they should be 
well tanned, free from lime spots and discoloration, and the 
grain should be as free from natural grease as possible. It 
is also necessary that the process of tanning used should yield 
a leather that is soft and full after it has been dried and staked, 
even though it is given very little fat-liquor or none at all. 
Complete neutralization of the acid in the skins is also of great 
importance. Even though acid dyes are applied, it is always 
best to neutralize the leather before coloring it. Where there 
is acid in the leather, the fat-liquor is imperfectly absorbed, 
the dyestuff is liable to be precipitated in the bath, and when 
finished the leather is likely to spew. If the skins are colored 
immediately after they have been neutralized and washed, the 
last washing should be in warm water, thus raising the tem- 
perature of the leather in anticipation of the dyeing process. 
The flesh side should be shaved smooth before the skins are 
colored. Where fat-liquoring is done previous to dyeing, it 
is essential that the liquor should penetrate completely into 



DYEING LEATHER 363 

the leather so that it does not leave the grain greasy or sticky. 
Before it is colored, the leather should be kept wet and pro- 
tected as much as possible from light. Dyeing may be accom- 
plished with acid dyestuffs direct, without mordant, or with 
basic dyes after the skins have been mordanted with tannin. 

Coloring with acid dyestuffs. — A practical method of color- 
ing with direct or acid dyes is carried out according to the 
following instructions : The skins, neutralized and shaved, 
are fat-liquored lightly, and then rinsed in warm water. 
Twelve gallons of water at 125° F. for each 100 lb. of skins 
is put into the drum, which is then started. The dyestuff 
solution is poured through the hollow axle into the drum and 
the leather is milled from 15 to 25 minutes. Where good 
penetration is desired, 1 or 2 oz. of ammonia should be added 
to the liquor in the drum. At the end of this time the dye- 
bath is acidified by the addition of formic acid. Enough acid 
should be used to neutralize the ammonia added, and in addi- 
tion to which, 2 parts by weight of formic acid for every 4 
parts of dyestuff, should be used. The acid thus added fixes 
the color on the leather by 10 minutes' longer drumming. 

To increase the fullness of the leather, some sumac or gam- 
bier liquor should be added to the dye-bath or run into the 
drum after the bath has been acidulated. This treatment is 
particularly advisable if the skins are to be glazed. 

The sumac liquor referred to is a decoction of 6 to 8 lb. 
of sumac leaves or sumac powder in 5 gallons of hot water. 
Two gallons of such liquor are used for each 100 lb. of 
leather. After 20 minutes a solution of 3 to 4 oz. of sulphuric 
acid, or three times as much sodium bisulphate in one gallon 
of water for each 100 lb. of stock is added gradually while 
the drum is turning, and the drumming is continued 10 or 
15 minutes longer. The colored leather is then rinsed and 
passed on for further treatment. The temperature of the 
dye-bath should be from 120 to 140° F. It is good practice 
to pass the skins through water at 140° F. before throwing 
them into the drum. 

The richest and fullest color results are obtained when 



364 PRACTICAL TANNING 

acid colors are topped with basic dyestuffs. This is done by 
adding a solution of 2 oz. or more of some basic color to the 
dye-bath as soon as all the acid color has been exhausted from 
the dye-bath. If this cannot be effected completely, the basic 
color is applied by drumming the leather in a fresh bath, in 
which case no further rinsing is necessary. 

Acid dyestuffs are dissolved by pouring boiling water over 
them and boiling to complete solution if necessary. The solu- 
tion is then passed through a piece of cheese-cloth or a fine 
sieve, and any particles remaining undissolved are brought 
into solution by pouring more boiling water over them. 
Formic acid is used in the dye-baths to get the full shade. 
The leather is not harmed when an excess of formic acid is 
used, as it evaporates during the drying of the leather. 

Coloring with basic dyestuffs. — Basic colors are applied to 
chrome-tanned sheepskins in the following manner : The neu- 
tralized and shaved leather is treated in a drum with a sumac, 
gambier, or fustic liquor. After this has been done, the dye- 
ing is proceeded with, the process lasting 20 minutes or 
longer at a temperature of 125 9 F. It is always advisable 
to add the solution of dyestuff in several portions through 
the hollow axle while the drum is turning. 

A decoction of 7 or 8 lb. of sumac leaves or sumac pow- 
der in 5 gallons of hot water is suitable for mordanting 
the leather. For very light shades, 6 quarts of such liquor 
is sufficient for 100 lb. of leather; for dark shades, from 8 
to 10 quarts. It should be strained before using. As the 
sumac bath alone does not fasten the tannin to the skin, a 
solution of tartar emetic (antimony-potassium tartrate) is 
generally used to overcome this uncombined condition and 
fix the color on the leather. After the skins have been treated 
with the sumac, the solution of tartar emetic is poured into 
the drum and the process is continued 15 minutes. The 
leather is then rinsed in warm water, the spent liquor run to 
waste, and the leather dyed with the basic color in an acid 
solution. From 8 to 12 oz. of tartar emetic is used for 100 lb. 
of leather. 



DYEING LEATHER 365 

Gambier mordant. — Two or three pounds of gambier for 
100 lb. of leather is another excellent mordant for basic dyes. 
Boil the gambier in 4 gallons of water, then add cold water 
to make 12 gallons of liquor. Use at 125° F., and drum the 
leather with it 30 minutes. Then dissolve 4 oz. of titanium- 
potassium oxalate in hot water, pour the solution into the 
drum and run 10 minutes longer. Drain off the liquor and 
proceed to color the leather with the basic dyestuff. 

Fustic or osage orange mordant. — Fustic extract is an ex- 
cellent mordant for shades of tan and yellow. Use from 2 
to 3 lb. for 100 lb. of leather. Dissolve in boiling water; then 
increase to 12 gallons by adding cold water and use at a tem- 
perature of 125° F. Drum the leather 20 minutes. Then 
dissolve and add 4 oz. of titanium salts and let the drum ro- 
tate 15 minutes longer. Drain off the liquor and color the 
leather with basic dyestuff. 

Two pounds of gambier and one pound of extract of fustic 
is also an excellent mordant for basic or acid dyes, and may 
be used with titanium-potassium oxalate the same as gambier 
or fustic alone. 

Sumac and titanium-potassium oxalate. — Four ounces of 
liquid extract of sumac may be used for each dozen small 
and medium-sized skins. The sumac is mixed with hot water 
and the skins drummed with the liquor for 20 minutes. Then 
pour the solution of titanium-potassium exalate (| to 1 oz. 
for a dozen skins) into the drum and run 10 minutes. Wash 
the skins and dye with basic colors, or dye them with acid 
colors without first washing. Dry powdered sumac may be 
used. The particles of sumac serve the useful purpose of 
taking up whatever grease there may be on the grain, as well 
as acting as a mordant by giving up tannic acid. 

Combined dyeing process. — Bottoming with acid dyestuffs 
or with diamine and anthracene colors, and then topping with 
basic dyes, is an excellent method of coloring chrome-tanned 
sheepskins, especially if they have damaged grain and it is 
desired to .cover up such defects as much as possible. The 



366 PRACTICAL TANNING 

coloring is usually done in two baths, namely, the bottoming 
and the topping bath. 

The leather is first drummed with the requisite quantity of 
fustic extract. The solution of acid dyestuff is then poured 
into the drum and drumming is continued another half-hour, 
and complete absorption of the acid dyestuff s is then brought 
about, if necessary, by the addition of 2 to 3 oz. of acetic 
acid per 100 lb. of leather, and then a solution of the basic 
dye added. 

Colors of superior fastness may be obtained by adding from 
4 to 8 oz. of sodium dichromate to the bath containing aliza- 
rine colors, finally adding acetic acid, and working the goods 
at as high a temperature as possible, say 150 to 160° F. The 
color solution is then drained out of the drum and the leather 
is topped with basic colors in a fresh bath. 

The skins are fat-liquored either before dyeing* or after 
topping. If the latter, they should be rinsed thoroughly before 
fat-liquoring. Acid, diamine, alizarine, and basic colors can be 
recommended for full, even, and rich shades. The quantity 
of dyestuffs required to color a lot of leather depends, of 
course, upon the color desired, the size and condition of the 
skins, and must be decided by the dyer. It is always wise 
first to try a few dyeing experiments on a small scale. 

Dyeing light shades with acid dyestuff s. — When light shades 
such as gray, drab, champagne, pea green, etc., are desired, 
the skins should be colored in the following manner : They are 
neutralized, shaved, weighed, treated in a drum with the solu- 
tion of acid dye, according to the shade, and then set with 
formic acid. An acid fat-liquor is poured in and the leather 
drummed 20 minutes. The procedure can also be reversed 
by first fat-liquoring the skins with an acid fat-liquor and 
dyeing afterwards. To secure complete penetration, all that 
is required is to neutralize the skins well and prolong the 
drumming. 

After the leather has been drummed a half-hour it is ad- 
visable to add a decoction of sumac or gambier to the bath 
after the fat-liquor has been exhausted by the leather, and 



DYEING LEATHER 367 

run the drum another half-hour. Where the color is added to 
the fat-liquor, which should be alkaline, from 2 to 4 oz. are 
used for 100 lb. of leather. Acid dyes are particularly suited 
for coloring light and fancy shades. 

Dyeing with direct colors. — These colors are of value to the 
dyer of chrome leather. After the skins have been neutral- 
ized and shaved, the solution of direct dye is applied, no 
mordant being required. After the leather has taken up the 
color, a solution of sodium dichromate or of copper sulphate 
should be poured into the drum for the purpose of setting the 
dye and making it faster to the action of the fat-liquor. A 
little salt added to the dye-bath will result in good shades. 
No acid is used and no re-tannage is necessary, and the 
leather should be perfectly neutral before it is colored. 
Direct blacks are used successfully with logwood, the leather 
being dyed first with this and then with the direct black. A 
good way to use these dyes for colors is to dye with them and 
then top off with basic dye. Direct dyes are especially use- 
ful for coloring leather which is finished dull or on the flesh 
side. It is best to use acid fat-liquor on leather colored with 
these dyes. 

Acid colors and sodium bisulphate. — About 100 lb. of 
leather can be nicely colored by using acid dyestuffs and so- 
dium bisulphate as follows : The required dyestuff is dis- 
solved in boiling water and made up to 12 gallons of liquor, 
which is used at 140° F. After the leather has been drummed 
20 minutes, 8 oz. of bisulphate is dissolved in hot water and 
added to the contents of the drum, which is run 10 minutes 
longer, when all the dyestuff will have been absorbed. The 
leather is then rinsed with warm water and. is fat-liquored. 
Complete penetration is obtained by adding 2\ oz. of ammonia 
to the dye-bath and drumming a half hour longer before add- 
ing the bisulphate. When this is done, the quantity of bisul- 
phate should be increased slightly to neutralize the ammonia. 

Coloring with phosphine dyestuff. — Tans and browns of 
good color and penetration are obtained on chrome sheep- 
skins by the use of phosphines and titanium-potassium oxa- 



368 PRACTICAL TANNING 

late. The procedure for 100 lb. of leather is as follows: 
Drum for 10 minutes with a solution of 3 oz. of oxalate. 
Then pour 1 lb. of fustic crystals in solution into the drum, 
and let the leather run 10 minutes. Then add 3 oz. more of 
the oxalate and drum 10 minutes. Rinse the leather, drain 
it, and color with phosphine blended with Bismarck brown, 
both of which are basic dyes, from 2 to 16 oz. of the phos- 
phine and from 1 to 4 oz. of brown according to shade desired. 

Fustic and logwood bottom. — A mixture of 2 lb. of fustic 
extract and 2 to 3 oz. of logwood crystals produces excellent 
results as a bottom for acid colors. After the desired shade 
has been secured, the skins are drained and treated either 
with acid fat-liquor or with an emulsion of "oil and egg-yolk. 
Topping acid colors with basic dye is one of the most ap- 
proved methods of getting tan and golden-brown shades. 
Formic acid added toward the end of the process increases 
the depth of color and fastens the color on the leather. 

Sumac and acid color mordant. — Full, rich shades of tan 
and brown can be secured by treating as follows: Drum the 
skins in a solution of 2 lb. of sumac extract and 6 oz. of 
acid brown aniline for 20 minutes. Then dissolve 5 oz. of 
titanium-potassium oxalate in a little hot water, pour the solu- 
tion into the drum and run it for 10 minutes. Wash the 
skins in two changes of water and color them with basic dyes. 

Practical formulas for popular shades: 1. Dark tan. — 
For 100 lb. of leather, drum 30 minutes with 1| lb. of phos- 
phine at 120° F. ; add 5 lb. of fustic extract in solution at 
120° F. and drum 30 minutes; finally pour 2 oz. of sodium 
dichromate at 120° F. into the drum, and run it 20 minutes 
longer; fat-liquor, set out, and dry the leather. 

2. A rich shade of chocolate brown is obtained in the fol- 
lowing manner: Boil 2 lb. of gambier and 1 lb. of extract 
of fustic in 4 gallons of water until dissolved, cool with cold 
water to make 12 gallons of liquor. Drum 100 lb. of skins 
for 30 minutes with this liquor; then pour 4 oz. of titanium- 
potassium oxalate dissolved in hot water into the drum, and 
run the skins 15 minutes longer. If the mordant has been 



DYEING LEATHER 369 

taken up by the leather, run off the liquor and pour the dye 
solution into the drum; if it has not been taken up, it is best 
to wash the skins before giving them the dye. For 6 dozen 
skins use 8 oz. of basic yellow and drum the skins 10 minutes ; 
then add 1 lb. of chocolate brown and 8 oz. of Bismarck 
brown, dissolved together and poured into the drum. Run 
the drum 20 minutes after the color has been put in; then 
wash and fat-liquor the skins, and hang them up to dry. Ex- 
tract of sumac may be used for the mordant if preferred. 

3. Golden-rod yellow, Bismarck brown, and champagne 
colors are efficient in dyeing chrome-tanned skins. A com- 
bination of golden-rod yellow and blue and brown produces 
a fine shade of tan. Mordant the skins with gambier and 
fustic, apply titanium salt, wash and dye with 20 oz. of auro- 
min, 8 oz. of Bismarck brown, and 8 oz. of methylene blue 
or malachite green. Drum 20 minutes, and the result is a 
fine, fast, and uniform shade of tan. 

4. An ox-blood color can be secured as follows : For each 
dozen skins use from 4 to 6 oz. of extract of fustic. Drum 
the leather 15 minutes with this. Then add to the liquor in 
the drum 2 oz. of tartar emetic for each dozen skins, and 
run 15 minutes longer. Wash the skins and prepare a color- 
bath at 120° F. Use from 2 to 3 oz. of amaranth 3R for 
each dozen skins and drum 20 minutes, then wash and fat- 
liquor the skins. The shade can be darkened by using 2 oz. 
of the amaranth and 1 oz. of chocolate brown for each dozen 
skins. A liquor made of fustic and peachwood extract is 
an excellent mordant for wine color. The skins are drummed 
in this for 20 minutes, when a solution of titanium salts is 
run in. Then they are drummed 10 minutes, washed, and col- 
ored with amaranth, to which a small quantity of malachite 
green has been added. 

5. Alizarine brown and fustic produce a fine shade of color 
for gloves, linings, etc. For each 100 lb. of leather, dissolve 
2 oz. of alizarine brown by boiling in 6 gallons of water. 
Add 6 gallons of cold water and use at 145° F. Drum 30 
minutes. While the skins are being drummed in the alizarine 



370 PRACTICAL TANNING 

dye, dissolve 1 quart of fustic extract in 1 gallon of hot 
water, and at the end of 30 minutes pour the solution into 
the drum and run 15 minutes longer. Drain off the spent 
liquor; wash, and fat-liquor. 

6. To color chrome sheepskins an attractive shade of green, 
drum a dozen skins with 4 oz. of sumac extract at 110° F. 
Then to the bath add 4 oz. of titanium salt dissolved in hot 
water for 100 lb. of leather. Drum 10 minutes. Drain off 
the liquor and color, using 3 oz. of either leather green special 
or dark green M and lJr oz. of amaranth 1R for each dozen. 
Drum the skins 20 minutes, wash, and fat-liquor. 

7. If a dark olive-green color is required, take the skins 
from the shavers and for each 100 lb. use 19 gallons of hot 
water and wash in this for 15 minutes; then drain the drum. 
Pour in 3 lb. of extract of fustic dissolved in 12 gallons of 
hot water and run 30 minutes. Make up a solution of 12 oz. 
of copperas and pour half of this liquor into the drum, and 
inspect the skins after 15 minutes. If they are dark enough, 
wash, and fat-liquor; if not dark enough, add more copperas 
liquor and drum 15 minutes longer; then wash the skins thor- 
oughly and fat-liquor them. 

Coloring after fat-liquoring. — Uniform results are obtained 
by coloring chrome sheepskins after they have been fat- 
liquored. Having been washed and shaved, mordant with 
gambier or with gambier and fustic, fat-liquor with acid fat- 
liquor, then color with aniline dyes, and dry them for finishing. 
This method of coloring is preferred by some dyers. The 
process can also be varied by fat-liquoring the skins first, then 
applying the vegetable tanning material and coloring with 
basic dyestuffs. Titanium-potassium oxalate may be used in 
the usual manner, and assists in obtaining uniform colors. 

The shades most in demand at present may be obtained 
with the following basic dyestuffs, which can be mixed as 
desired : paraphosphines, Bismarck browns, leather browns, 
Russian red, and ox-blood A and B ; for darkening the shade, 
or for saddening basic colors, use neutral blue and solid green 
crystals. 



DYEING LEATHER 371 

Acid colors for shades of tan and brown are Indian yel- 
lows, acid phosphine, and Havana brown; and for ox-blood, 
new red B, roccelline mixed with Havana brown or acid 
phosphine J I. For saddening the shade or as a sad- 
dening agent for acid colors, use naphthol black B and fast 
acid green B. 

Flesh-finished chrome sheepskins. — For some purposes, 
sheepskins finished on the flesh side with a soft, velvety finish 
are required. Skins that have defective grain are used for 
this class of leather, since the value of the leather does not 
depend upon the quality of the grain. The leather is made 
by the usual methods of chrome tanning, but instead of being 
finished on the grain, the skins are dressed smooth and vel- 
vety on the flesh side. 

After the skins have been neutralized and washed they 
are put into a drum with 4 gallons of water and 5 lb. of 
pipeclay for 100 lb. of leather, and are milled for 20 minutes. 
They are then run on a wet wheel which gives a good face 
to the leather. After this has been done they are run in warm 
water and then colored. Coloring is done in the same manner 
as on grain-finished skins. Fustic, gambier, and sumac are 
used as mordants for basic dyes. Wood dyes are also used 
in conjunction with titanium salt. A satisfactory method of 
coloring is to apply acid dyestuffs in a drum. Good penetra- 
tion is essential on this leather, and it is helpful to add 1 to 2 
oz. of ammonia to the dye liquor. At the end of 20 or 25 
minutes, 2 parts by weight of formic acid for every 4 parts 
by weight of dyestuff are added to the drum to acidify the 
bath. A little more than this quantity of acid may be neces- 
sary to neutralize the ammonia previously added. The leather 
is drummed 10 minutes longer. Some sumac or gambier 
liquor added after the bath has been acidulated imparts a 
feeling of fullness to the skins. As a fat-liquor, an emulsion 
of egg-yolk, olive oil, castile soap, and flour is especially suit- 
able; but a less expensive liquor can be used. The skins, after 
coloring, are washed and fat-liquored. 

Drying and staking are carried out in the usual manner. 



372 PRACTICAL TANNING 

Staking on a machine should be followed by knee-staking to 
eliminate all stretch. The skins should then be given a light 
buffing on a very fine emery wheel, and are then ready to be 
trimmed and sorted. If the work has been properly done, 
the skins finish soft, are evenly colored, and have a smooth, 
velvet-like face. 

If white skins are required, the tanning process is followed 
by treatment with flour ; fat-liquoring and finishing being done 
as already described. 

Coloring chrome-tanned sheepskins after fat-liquoring and 
drying out. — Chrome sheepskins take color well before they 
have been fat-liquored and dried, but it is generally considered 
impracticable to dye such skins after they have been dried 
out. However, this has been proved to be incorrect, as good 
results may be secured in the following manner : 

After the skins have been fat-liquored and dried out they 
are soaked and are ready for dyeing. This is best effected 
in a drum fitted with steam pipes ; neither the paddle nor the 
tray are suitable without some arrangement for keeping the 
dye hot. Dyeing is best carried out at a temperature of 
140° F. 

The method is as follows, for a dozen skins: 8 to 10 oz. of 
the dye is carefully weighed out into a wooden tub and dis- 
solved by pouring on it about 200 times its weight of boiling 
water, stirring briskly. Then 8 to 10 oz. of sodium bisulphate 
is dissolved in hot water in a separate vessel. Half of the 
concentrated dye solution is now added, with the bisulphate 
solution, to enough water at 140° F. in the drum to cover 
the skin. The leather is placed on the shelf, and the drum 
is started. After running 'the goods in this dye-bath for 15 
minutes, the remainder of the dye solution is added and mill- 
ing is continued for 30 minutes longer, or until the goods have 
attained the depth of shade required. After dyeing, the skins 
are washed in warm water, set out, lightly rubbed over the 
grain with glycerine, and dried out while strained on boards. 

Blacking with hematin and direct chrome black. — A fine rich 
black is obtained on chrome sheepskins by the following 



DYEING LEATHER - 373 

method : Dissolve 1 lb. of hematin crystals for 100 lb. of 
leather in 4 gallons of boiling water, add 6 or 8 gallons of 
cold water and a little ammonia to make it slightly alkaline, 
and use at a temperature of 125° F. After the leather has 
been run in this dye for 15 minutes, add 1| lb. of chrome 
leather black dissolved in 5 gallons of boiling water to the 
liquor in the drum, and run the leather 15 minutes longer. 
Drain the drum and pour in the fat-liquor ; then run the drum 
for a half -hour; wash the skins in warm water, set out, oil the 
grain lightly with neat's foot or mineral seal oil, and hang 
up to dry. 

Sheepskins which are to be given a glazed finish, are bene- 
fited by a light re-tannage with gambier before they are dyed. 
This assists in getting a fine color and finish, and makes the 
leather less stretchy. The skins may be paddled or drummed 
in the gambier liquor. 

Blacking zvith logwood and titanium-potassium oxalate. — 
In this process of dyeing, logwood extract or crystals, titan- 
ium salt, and direct chrome black are used, the quantities given 
below being for 100 lb. of shaved leather. Drum the leather 
in a Solution of 3 oz. of titanium-potassium oxalate for 10 
minutes, then pour in a solution of 2 lb. of logwood, -J lb. of 
chrome leather black, and 4 oz. of ammonia in 12 gallons of 
water. Drum the skins in this liquor for 20 minutes; then 
pour in a solution of 3 oz. of titanium-potassium oxalate and 
allow the drum to run 10 minutes longer. Then either drain 
the drum and run in the fat-liquor, or wash the skins and 
then fat-liquor. 

Blacking with direct chrome black. — Put the leather, neu- 
tralized and shaved, into the drum with 10 gallons of water 
at 125° F. for each 100 lb. Run for a few minutes, then pour 
the solution of dyestuffs through the hollow axle of the 
drum. Dyeing will be completed after about a half-hour's 
drumming. For blue-black with a blue flesh side, use from 
1 to 1 1 lb. of chrome leather black. It is advisable to add a 
small quantity of logwood liquor to the dye-bath after a short 
drumming to fill the leather somewhat. 



374. PRACTICAL TANNING 

Fat-liquoring may be done either before, during, or after 
dyeing. If the fat-liquor is added to the dye-bath it is ad- 
visable to drum the leather in the dye liquor for 15 minutes 
before adding the former. Another method of blacking with 
direct chrome leather dyes is as follows : Use 4 or 5 oz. of 
nigrosine G and 4 oz. of chrome leather black C for 100 lb. 
of leather. This produces the desired fine grain black and 
the blue-black flesh. Chrome leather black C used alone also 
produces blue-black flesh and black grain. The leather, thor- 
oughly neutralized and treated with alkaline fat-liquor, is dyed 
for 30 minutes in a drum with 2 lb. of dye for 100 lb. of 
leather, at a temperature of 120 to 140° F. 

By dyeing first with 8 to 10 oz. of chrome leather black 
C for 20 minutes, then adding 1 oz. of acetic acid and 10 min- 
utes later a solution of 8 oz. of leather black T B, drumming 
the leather 10 minutes more, and then fat-liquoring, a fine 
color is secured on both flesh and grain sides. A' lit- 
tle logwood extract liquor added to the dye is beneficial, in- 
creasing the fullness of the leather. 

Methods of dyeing vegetable-tanned skins: Blacking 
vegetable-tanned skins. — There are many methods of dyeing 
black on gambier, quebracho, sumac, or combination-tanned 
leather. One of the newer and better processes is by the use 
of logwood and titanium-potassium oxalate. Drum the skins 
in a solution of 4 oz. of the titanium salt for 100 lb. of dry 
leather; next pour slightly alkaline logwood or hematin liquor 
— made by dissolving 4 lb. of liquid extract in 5 gallons of 
water — into the drum, and after the leather has been treated 
with this for 15 minutes, pour in 4 oz. more of the titanium 
salt; drum 10 minutes longer, then wash and fat-liquor. No 
copperas, iron liquor, or other striker is required. The titan- 
ium-potassium oxalate after logwood produces a soft, deep, 
and permanent black. 

When soft black leather is wanted, the following procedure 
may be adopted : Take the skins out of the tan liquor, wash, 
and press them. Then treat with acid fat-liquor, or with an 
emulsion of soap and oil, and dry out in the usual manner. 



DYEING LEATHER 375 

When dry, soften the skins with warm water and dye as al- 
ready described; then wash and dry for finishing A few 
ounces of fustic paste or crystals boiled with the logwood 
makes the black deeper and richer. For some purposes the 
skms work out sufficiently soft without being fat-liquored, 
but if soft leather is desired, they should be fat-liquored im- 
mediately after tanning, or after they have been colored 

there are several direct blacks obtainable which dye the 
leather a deep black without the use of logwood. When the 
flesh side has to be colored, the skins are drummed with the 
solution of dyestuffs; and when it is to be left uncolored the 
black is applied by hand to the grain side only. If the flesh 
side is to remain undyed, the staining process is to use a solu- 
tion of direct black heated to 125° F. and applied directly 

suffidenf am mCanS ° f " brUSh - UsUElly tW ° COats are 
If the flesh side is to be colored blue, purple, or blue-black, 
the skins are drummed with the solution of black and then 
stained on the grain with the same dye, washed, and dried 
For leather that is to be given a glazed or other bright finish 
a black with a greenish cast is preferred 

Dyeing zvith acid and basic ^^.-Fancy-colored skins 
must have clear and uniform colors to give satisfaction, but 
it is not an easy matter to get such colors unless the grain is 
sound and free from excess of tannin. Tanning should be 
done in clean liquors, and all excess of tannin should be elim- 
inated before coloring is started. The dye, especially a basic 
dye, quickly strikes defective spots in the grain, and on ac- 
count of the precipitation of the dye on such spots, and the 
darker coloring resulting therefrom, the finished leather shows 
an unevenly colored grain which detracts from its value Tar- 
tar emetic is useful in removing surplus tannin from the grain 
fixing the dye on the leather, and getting uniform shades' 
Basic dyestuffs are also deposited on the skins rapidly which 
often causes uneven coloring. Acid dyes color more' slowly 
than basic dyes, and more time is therefore required for the 
production of well developed shades; but the colors are gener- 



376 PRACTICAL TANNING 

ally more uniform and more permanent, and the defective 
spots do not show as plainly as when basic dyes are used. 

The skins are usually dried after they are tanned, and are 
softened and washed and cleared before they are colored. 
They are shaved to secure uniform thickness. When the wash- 
ing is properly done, the colors are clear, full, and deep. The 
dry skins are moistened in a tub, and left in piles for some 
hours to become soft and wet; or they may be moistened in 
a drum. The water used for this work should be soft and 
warm, as such water has greater softening and cleansing 
power than cold water. A safe temperature is from 85 to 
95° F. The skins are washed until soft and clean. 

Sorting for black and colors is best done before the skins 
are washed. The light shades require leather free from de- 
fects, while the dark shades allow of a certain amount of 
covering from the dye-bath. 

Coloring with artificial dyestuffs. — Sumac freshens up the 
skins so that they readily take the dye liquor, therefore, 4 oz. 
of sumac extract for each dozen skins is placed in the mill and 
the skins are drummed in this solution for 20 minutes. To 
clear the grain and set the dye, a solution containing 2 oz. 
of tartar emetic for each dozen skins is poured into the drum, 
and the skins are run 15 minutes longer. After this it is 
best to rinse the skins in warm water, drain the drum, and 
return the skins to color them. From 2 to 4 oz. of dyestuff is 
required by each dozen skins. The temperature of the dye- 
bath should be about 100° F. Fustic may be used instead of 
sumac. Either basic or acid dyes may be used on the skins 
prepared in this manner. Dyeing is usually commenced by 
entering the skins in a weak dye-bath, which is gradually 
brought to full strength. A fairly even temperature of 120° 
F. should be maintained, and on this account it is advisable to 
heat the skins in hot water before passing them into the dye- 
bath. Some dyers color with acid colors and then top off with 
basic colors. When this is done, it is best to apply the basic 
dye in a fresh bath so that there may be no precipitation of 
the dyestuff in the liquor. 



DYEING LEATHER 377 

Another method of preparing the skins for dyeing is as 
follows : The dry leather is moistened and softened, then run 
in a solution of 8 oz. of titanium-potassium oxalate for every 
100 lb. of dry skins. Drumming with this solution for 10 
minutes gives a yellow base on which any shade of tan, 
brown, ox-blood, etc., can be easily obtained. 

If acid dyes are to be used, the skins may be colored at the 
end of 10 minutes without being washed; if basic dyes are to 
be applied after the drumming in the titanium solution, the 
liquor should be run off, and the skins washed and then put in 
the dye liquor. 

Where extract of fustic is used as a mordant, 1| pints dis- 
solved in a pail of boiling water should be used for 100 lb. of 
leather. The skins, together with enough water to float them, 
are put into the drum which is set in motion. The fustic solu- 
tion is next slowly poured in, and drumming is continued 20 
minutes. A solution of 4 oz. of titanium-potassium oxalate 
is then added to the liquor, and the leather is run 15 minutes 
longer. The skins can then be either fat-liquored and dyed, 
or dyed first, and then fat-liquored. 

After the leather has been running in the solution of acid 
dyestuff for 20 minutes, 4 oz. of formic acid for each 100 
lb. of leather is poured into the dye-bath to exhaust it on 
the leather ; the drum is run 10 minutes longer, and the skins 
are then rinsed and fat-liquored. 

Ox-blood shade. — 1. For 100 lb. of dry leather previously 
treated with sumac, use 8 oz. of titanium-potassium oxalate. 
Soften the skins with warm water and drum them in the solu- 
tion of titanium salt at 95° F. for 10 minutes. Drain the drum 
and rinse the skins; then dye them. One dozen skins of aver- 
age size require about 6 oz. of amaranth 3R and -§ oz. of mala- 
chite green. Dissolve these dyes in 1 gallon of hot water, 
add 7 gallons of cold water, apply to the skins at 100° F., and 
drum 15 minutes; then wash and fat-liquor. 

2. Directions for coloring 10 dozen skins : Moisten with 
warm water, and run in the drum with water at 90° F. Dis- 
solve 3 lb. of tartar emetic in hot water. Pour the solution 



378 PRACTICAL TANNING 

into the drum, and run the drum 15 minutes; then drain off 
the liquor. To color, use 4 lb. of amaranth 3R, adding to 
the skins in four portions at intervals of 10 minutes. Then 
add 1^ lb. of amaranth 1R with 8 oz. of chocolate brown, and 
run the drum a half-hour. Drain off the liquor, run in the fat- 
liquor, add 10 oz. of potassium bichromate, and let the drum 
revolve 10 minutes longer; then wash the skins and dry for, 
finishing. 

3. A good shade of ox-blood can be obtained on vegetable- 
tanned skins in the following manner: Boil 10 lb. of hyper- 
nic chips and strain the liquor. Put the skins in drum with 
water at 90° F. Add the hypernic solution while the drum 
is running, and mill the skins for a half-hour. Dissolve 7 
oz. of amaranth 3R in 1 gallon of water. Strain the solu- 
tion through cheese-cloth and cool to 110° F. by adding cold 
water. Apply this to the leather in three portions at intervals 
of 5 minutes, running the drum 15 minutes after the last of 
the dye is added. Drain out the spent dye liquor, rinse the 
skins in clean, warm water, and then drum with a solution 
of 3 oz. of ootassium bichromate for 15 minutes and finally 
fat-liquor. 

Brown shades. — 1. Mordant the skins with sumac and 
titanium-potassium oxalate, then dye with 1 oz. of leather 
brown F for each large skin, and less for smaller ones. Drum 
the leather for a half -hour, wash, and fat-liquor. 

2. Another excellent shade of brown can be obtained by 
drumming the skins in a solution of titanium-potassium oxa- 
late for 10 minutes; drain the drum and add the color solu- 
tion made of 4 oz. of phosphine, \ oz. malachite green, and 
^ oz. methyl-violet 2 B; and run the leather in the dye for 15 
minutes, finally washing and finishing it. 

Tans and browns, all shades, are produced by the following 
method: For each 100 lb. of dry leather, sumacked, washed, 
and cleaned, use 1 to 3 lb. of phosphine and 1 to 8 oz. of 
Bismarck brown, according to the depth of shade required. 
Drum the leather in the color-bath for a half-hour, or until 



DYEING LEATHER 379 

it is exhausted. Add 4 to 10 oz. of titanium-potassium oxa- 
late dissolved in hot water, and drum 10 minutes more and 
rinse well. If not previously fat-liquored, apply such liquor 
and dry the skins for finishing. 

Tartar emetic may also be used on the skins after they 
have been run in the sumac liquor, the goods then being 
washed and colored. Leather which is dark, greasy, and dirty 
can be much improved by using borax and sulphuric acid. 
Put the skins into the drum with warm water containing con- 
siderable borax, and wash them 20 minutes. Drain off the 
borax bath and put warm water acidified with sulphuric acid 
into the drum, and wash the skins 10 minutes, rinse in clean 
water, make a sumac bath strong and hot, add a little salt 
to it, and drum the leather in this for 30 minutes; rinse in 
warm water, and strike out the leather for coloring. Run 
it in warm titanium solution, then in the dye, rinse, and finish. 

Dyeing with fancy effects. — By a special preparation or by 
manipulation of the leather, or by suitable application of the 
dyestuff, a great variety of effects may be produced, of which 
those described in the following notes meet 'the present de- 
mands of fashion. 

Marbled effects. — These are obtained by folding the moist 
leather prepared for the dyeing into a great number of irreg- 
ular pleats, and pressing the pleats so formed as firmly and 
as closely together as possible, whereupon the leather is dyed 
either by spraying on the dye, or by placing it on a metal 
plate and dipping it quickly into the liquor. This must be 
done rapidly. The leather is then rinsed in pure water kept 
ready. The greatest variety of effects may be obtained by re- 
peating the operation several times with different color solu- 
tions, and the effect may still further be varied by treating in 
like manner leather previously dyed a uniform shade. The 
method of dressing which follows is the same as usual. 

Spray dyeing. — This is carried out with various dyestuff 
solutions by means of a blowpipe provided with a fine noz- 
zle, the leather being spread out flat on a table or hung on 



380 PRACTICAL TANNING 

hooks. There is of course plenty of scope for a great variety 
of effects, according to the dyestuff solutions applied, the 
leather, if desired, being previously dyed to some uniform 
shade, or stencil plates are used, which again varies the effects 
obtained by this process. To ensure good fastness to rubbing 
and water, solutions of color soluble in alcohol, with the ad- 
dition of some shellac, are frequently used for spraying. 
"Changeant" dyeings are produced by spraying the color solu- 
tion sideways onto the previously pressed leather, the side 
opposite to the pressed parts thus remains either undyed, or 
is sprayed over with a different color solution. 

Antique leather. — This method is also frequently applied 
for producing so-called antique leather. The rough, irreg- 
ular, and wrinkled effects in favor for leather of this descrip- 
tion are produced by pleating the skins and crushing them up 
tightly in sacks, or nets, treating them in strong tanning solu- 
tions, and only opening the bundles to complete the tanning, 
when there is no longer any fear of the wrinkles disappearing. 
The antique grain may also be imparted to the leather by em- 
bossing. In dressing leather of this kind, the wrinkles should 
be well preserved and superfluous setting-out avoided. 

Various methods are applied for producing antique effects, 
for instance: The raised portions of the grain of the pre- 
viously dyed and dried leather are buffed by means of fine 
emery paper or pumice. The raised portions of the surface 
of the previously dyed and dried leather are given a coating 
with a "fatty resist" consisting of wax and vaseline, where- 
upon the deeper portions are dyed by means of a soft sponge 
or a brush, or by spray dyeing. All parts protected by the 
"wax resist" remain undyed. Any excess of dyestuff which 
may be present is then removed with a moist sponge and the 
leather is dried. The dyestuff intended to stain the deeper 
portions of the grain has to be applied in a rather highly con- 
centrated form, owing to its rapid absorption, and it is advis- 
able for such purpose to use acid dyestuffs or basic colors 
which have no tendency to bronze. The wax resist may, if 
necessary, be replaced by collodion varnish. 



DYEING LEATHER 381 

If collodion varnish colored with cerasine and mineral col- 
ors are used for dyeing the deeper portions of the grain of 
the previously dyed and dried leather, the leather is first given 
a coating of thin Irish-moss decoction. When dry, suitably 
stained collodion varnish is applied, which, after being allowed 
to dry for a short time, is removed from the raised portions 
of the grain by means of a linen pad dipped into amyl-acetate 
and pressed out well, the bottom shade then reappearing. 
Antique effects may likewise be obtained in the reverse man- 
ner by dyeing the raised portions of the grain with colored 
gelatine, shellac dissolved in spirits, or collodion varnish, the 
deeper parts of the grain thus retaining the original shade. 
By clever manipulation, exceedingly handsome and entirely 
original effects may be produced. When using collodion 
varnish it is better to add some castor oil, in which the dye- 
stuff may be dissolved, to enhance the pliability of the leather. 

Shellac dissolved in spirits may be colored with basic col- 
ors or with dyestuffs soluble in spirits, and collodion varnish 
with cerasine colors and the addition of mineral colors, to 
any desired shade. 

To remove from the leather the smell peculiar to collodion 
varnish with which it has been treated it is hung up for some 
time in a well-ventilated room at a temperature of 110° F. 
The subsequent dressing is the same as for colored leather. 

Bronze dyeings (dyeings with metallic luster). — The leather 
is first dyed in the tray with a solution containing 1 to \\ 
oz. of some suitable basic color to \\ gallons of water (dis- 
solved with the addition of alcohol), then rinsed, and topped 
with a solution containing up to 2 oz. of a suitable acid color 
per 1^ gallons. It is better to treat such leather before dye- 
ing with a solution of tartar emetic. After this dyeing in 
the tray, the leather is struck out on the flesh side, the grain 
being oiled lightly with linseed oil, and dried. The subse- 
quent glazing may be facilitated by lightly rubbing the grain 
side, immediately before the glazing, with a cloth containing 
a little linseed oil. 



382 PRACTICAL TANNING 

The following is another method of producing bronze dye- 
ing of particularly good resistance to water: The leather is 
first dyed as desired with a strong solution of basic color. 
After drying, it is glazed by machine, and then coated with 
a stained collodion varnish diluted with about half its weight 
of amyl-acetate, and then dried. This treatment is repeated 
if necessary, and yields an intense bronze luster, which may 
be still further enhanced by severe glazing. For so-called 
velvet or antelope shades a very deep penetration is required 
as a rule. This effect is produced on buffed, bark-tanned and 
sumac-tanned cowhides and calfskins, or are imitated by dye- 
ing the flesh side of bark-tanned sheepskins. This is ensured 
to best advantage by working according to the following 
method : The leather is first prepared like other colored 
leather, buffed in a dry state, and soaked. It is then dyed 
warm in the drum with acid colors, some ammonia being 
added at the beginning of the operation. The material is 
dyed for about an hour, the requisite quantity of formic acid, 
up to ^ per cent, being added towards the end of the dyeing 
operation. The leather is then rinsed thoroughly, set out, 
oiled, and dried. Some shades, especially black, may be pro- 
duced to good advantage by topping the acid colors with basic 
colors. Black, for instance, is produced by dyeing with 2 per 
cent of nigrosine, shaded if necessary with other dyestuffs, 
the acid being added after about an hour's dyeing, and the 
leather topped with 1 per cent of leather black T B or velvet 
black B, and some alum or acetic acid. The leather is then 
dyed for about another 20 minutes, rinsed, set out, oiled, and 
dried in the usual manner. 

When dyeing these leathers by the staining process, the 
solutions of acid colors are brushed on without the addition 
of acid ; the leather is then dried, and the second coloring ap- 
plied, this time with the addition of formic acid in order to 
fix the acid color. A dense shade of black is produced with 
about 1 lb. of nigrosine, shaded if necessary with orange, etc., 
and the addition of 8 oz. of formic acid for 10 gallons of 



DYEING LEATHER 383 

dye liquor, the leather being then dried. This treatment is 
followed by the application of another solution of 1 lb. of 
leather black T B in 10 gallons of staining liquor. A pre- 
paratory treatment with titanium-potassium oxalate, and an 
after-treatment if necessary with a tanning solution, enhances 
the fastness to rubbing. 

Coloring and finishing India-tanned skins. — India-tanned 
sheepskins and goatskins in various colors and finishes are used 
for the manufacture of shopping-bags, traveling-bags, belts, 
collar-boxes, bookbindings, carriage trimmings, linings, etc., 
and in making leather novelties and specialties. They can be 
finished with any kind of grain, in any color, glazed or dull, 
smooth-grained or embossed; they can likewise be made soft 
or firm as may be desired. Large, heavy skins are used for 
suitcases and bags ; the smaller ones for purposes where light, 
soft leather is suitable. Bookbinders use India skins in a 
variety of colors, the staples being pebbled grain, dark green, 
dark blue, wines, and blacks. As bookbinders' leather must 
be fairly thin to cover the backs and corners of books, the 
skins are split to the thickness required. 

Washing. — The water used should be at a temperature of 
90° F., and its efficacy is enhanced by adding some borax 
or washing soda, from 2 to 3 lb. for 100 gallons of water. 
The skins are washed in this solution for 15 or 20 minutes, 
then in clear water and made ready for further treatment. 
It is necessary to re-tan the skins with some tannage that 
makes soft and light-colored leather; and if for light shades, 
it is necessary to bleach the skins with acetic acid after the 
borax bath. The borax cleanses the skins perfectly, but 
darkens the color; the acid-bath serves to brighten up the 
color. The skins are drummed in the acid solution (from 2 
to 3 oz. of acid per gallon of water may be used), then washed 
thoroughly to remove every trace of it, when they are ready 
for the sumac treatment. 

Re-tanning zvith sumac. — The sumac liquor should be 
strong and at a temperature of 105° F., and the leather should 



384 PRACTICAL TANNING 

be treated in a drum or in a paddle. One to two pounds of 
sumac should be used for each dozen skins. The leather is 
run in this sumac liquor for 30 minutes to an hour, after 
which it is washed in warm water, struck out with a slicker, 
and hung up to dry. When dry, it can be dyed any shade 
of color. 

Instead of sumac, quermos extract may be used, as it pro- 
duces a light color and is stainless. After the washing from 
the re-tan, the skins have a good color and for some purposes 
they can be finished without dyeing. The borax removes some 
of the tanning material and much of the natural grease. The 
acid bath brightens the leather and the sumac replaces the tan 
washed out, thus making the skins softer and the grain better 
prepared for subsequent dyeing. Some tanners use sodium 
hyposulphite in the wash-bath in place of borax, 10 lb. being 
dissolved in a barrel of hot water; the solution is used at 
110° F., and washing for a few minutes, only. The use of 
normal sodium sulphite, or the tri-calcium phosphate, with 
acetic acid, to clear the skins before going into the sumac, is 
somewhat milder and gives satisfactory results. 

Coloring the skins. — To prepare the dry leather for color- 
ing it is moistened with warm water. For single pairs of 
skins the tray is used, while for larger quantities the drum 
is necessary. 

The dyeing process is usually begun by entering the skins 
in a weak dye-bath, which is gradually brought to its full 
strength. For single pairs, 8 or 10 minutes is sufficient; for 
larger numbers, from 15 to 30 minutes should be allowed. 
A fairly even temperature of about 115 to 120° F. should be 
maintained, and on this account the skins are sometimes heated 
before they are placed in the warm liquor. The weights of 
dyestuffs are calculated on the number of skins, the average 
size being generally taken. Light shades require 1 to 14 oz., 
medium shades If to 2\ oz., and full shades up to 5 oz. per 
dozen. 

L One method of coloring the skins is as follows: They 



DYEING LEATHER 385 

are run in a drum with warm water until they are soft and 
open. For each dozen skins from 2 to 5 oz. of tartar emetic in 
solution is added, and the drum is run 15 minutes. This clears 
the grain and sets the tannic acid. The water is then drained 
out of the drum and the skins are colored with basic dyestuffs. 

2. Another process is to drum the skins for 10 or 15 min- 
utes in a warm solution of 6 to 8 oz. of titanium-potassium 
oxalate for each 100 lb. of dry leather, then rinse and apply 
the dye. This process is recommended, since it mordants 
with titanium tannate, itself a yellowish shade, on which bot- 
tom all shades of tan, brown, green, blue, and maroon can 
be easily obtained. After running off the liquor, a slight rins- 
ing with warm water is advisable but not always necessary. 
If acid dye is to be applied, the rinsing may be omitted; if 
basic dye is to be used, it is necessary to wash the skins only 
when the mordant bath has not been fully exhausted. After 
the desired shade is obtained, the leather is washed and 
finished. 

The dyed skins which are to be glazed subsequently should, 
on leaving the liquor, correspond approximately in shade with 
the dry pattern; if they are to remain dull or are to be glazed 
but lightly, a wet portion of the pattern should be used for 
matching. After dyeing, the leather is rinsed, set out, and 
tacked on boards. 

Dyeing the skins black. — 1. India-tanned skins can be 
blacked through flesh and grain by using logwood and titan- 
ium-potassium oxalate. A fairly strong logwood liquor, 
slightly alkaline, should be used, and 10 oz. of titanium salt 
for 100 lb. of dry leather. Dissolve the latter and drum the 
leather in the solution for 10 minutes, then drum with the 
logwood liquor for 15 minutes. No copperas or iron liquor 
is used, as the logwood and titanium-potassium oxalate dye a 
deep, permanent black. It is advantageous to use logwood 
crystals and add a little fustic paste to the liquor to intensify 
the black. 

2. To dye flesh and grain of the re-tanned leather, the skins 



386 PRACTICAL TANNING 

should be first drummed in a solution of methyl-violet and 
then in a basic black solution. For 250 lb. of dry leather, 
8 oz. of methyl-violet and 5 or 6 oz. of basic black are re- 
quired. Drum in the violet solution for 20 minutes, then 
for 15 minutes in the basic black liquor to which 4 oz. of 
titanium salt in solution has been added, wash and finish. 
3. Where the flesh side of the skins is to be left uncolored, 




Figure 96. — Top pan blacking machine used for seasoning and coloring. 

or to be dyed black or dark blue, tHe use of the direct leather 
black can be recommended. 

If the flesh side of the skins is to be left undyed, the black 
is applied to the grain side by the staining or brushing proc- 
ess. The dye solution consists of 1 lb. of dyestuff and 8 
oz. of acetic acid in 10 gallons of water. The dye liquor 
should, during its application, be kept at 130° F., and be 
thoroughly brushed into the grain. Usually two applications 
are sufficient for dry leather. 

4. If the flesh side of the leather is also to be dyed, direct 
leather black is applied in a paddle or drum, preferably the 
latter. Usually 1| lb. of the dyestuff per 100 lb. of leather 



DYEING LEATHER * 387 

is required, to which 3 to 5 oz. of acetic acid is added with 
the necessary volume of water. 

5. Where the flesh side of the skins is to be dyed dark 
blue and the grain black, the leather is first dyed with the 
direct black in a drum for half an hour at 115° F. It is 
then strongly set out, and after having been dried, is dyed 
on the grain by the staining or brushing method with the 
same material. 

6. The skins can also be flesh-colored by the use of blue 
nigrosine. For each dozen skins, 2 to 3 oz. of nigrosine is 
dissolved in hot water and applied at 110° F. The skins are 
drummed in the solution for 20 minutes, and then blacked 
on the grain by hand or on a machine with logwood and iron 
liquor. 

7. The leather can also be dyed by being first drummed in 
logwood liquor and then the color developed in the drum by 
the addition of iron liquor, or by passing the leather through 
the grain-blacking machine shown in figure 96. 

Drumming the leather in a warm solution of sulphonated 
oil or adding the oil to the logwood liquor increases its soft- 
ness and improves its texture. 

Ooze leather. — This is prepared by snuffing the grain until 
it has a soft, velvety appearance. Dyes for ooze leather should 
be selected for their penetrating power. Excellent results in 
coloring sheepskins may be obtained by dyeing first with acid 
colors, as, for example, dyeing coffee shades, first with In- 
dian yellow G; tan shades, first with orange extra; and red- 
brown shades, first with fast brown B N, and then topping 
with the proper mixture of diamine phosphine J. Bismarck 
brown E E, methylene blue B B, or new blue R. 

The acid dyes produce an excellent level bottom for the 
basic colors. Light pearl, gray, champagne, blue, and helio- 
trope are most successfully obtained with easily leveling dyes, 
such" as cyanole fast green, cyanole F F, lanafuchsine S 
G and S B, orange extra, and acid yellow A T. These dyes 
give also good fastness to light. 



388 PRACTICAL TANNING 

Coloring chamois leather. — Dyeing this class of leather is 
not as simple a process as dyeing vegetable-tanned skins. The 
oil-tanned fibers do not take up the dye readily unless the 
skins have been previously mordanted. The most common 
mordants used for this class of goods are chrome-alum and 
potassium dichromate, especially when alizarine dyes are used. 
The leather must be wet back with warm water, and the ex- 
cess of oil removed. For this purpose the goods are drummed 
in a solution of washing soda at 95° F. ; an excess of soda 
is not very harmful unless the temperature is too high, a suit- 
able strength being about 2 per cent. When the grease has 
been removed in this way, the goods may be fat-liquored 
lightly and dried out. If the skins are for light shades, they 
can. be bleached with sodium peroxide and sulphuric acid, or 
with potassium permanganate and sulphurous acid. When 
the goods have been dried, they are fluffed on one side and 
again wet-down. Mordanting with chrome-alum follows, 
which is best done in the drum. The chrome-alum is dis- 
solved to make a 1^ to 2 per cent solution, and this liquor 
placed in the drum with the goods, about 25 gallons being 
sufficient for 6 dozen skins. Drumming is continued until 
the chrome-alum has entirely penetrated the thickest parts, 
which usually takes from 30 to 40 minutes. When the mor- 
dant has penetrated the goods they are ready to be dyed. 
For this purpose it is customary for the dye to be added to 
the mordant bath without running it away, but it is better to 
remove the goods from the mordant bath and treat in a fresh 
dye-bath. 

As already stated, alizarine colors are used for this class 
of goods. The dyestuff should be dissolved in boiling water, 
and the color developed by the addition of sodium bisulphate 
at a temperature of 115° F. Half of the dye to be used is 
added to the drum and the goods are milled for 20 minutes. 
The quantity of bisulphate then added is about twice the weight 
of the dye-stuff used, and the remainder of the dye is intro- 
duced. Drumming is continued for 20 minutes, when the 
goods should be thoroughly dyed, the color having penetrated 



DYEING LEATHER 389 

completely through the fibers. After fat-liquoring and drying, 
the goods are ready for finishing. 

Dyeing chrome-tanned calfskins black: 1. Dyeing with 
logwood and direct leather black. — The use of a direct chrome 
leather black, combined with logwood or some product of 
logwood, is the most approved method of dyeing chrome 
calfskins black. A typical formula is : hematin crystals, 1 lb. ; 
ammonia, 1 oz. ; and chrome leather black C, 1| lb. for each 
100 lb., shaved weight. 

The skins are thrown into the drum together with 8 or 
10 gallons of warm water. The logwood or hematin liquor, 
made by dissolving the dye in 2 or 3 gallons of boiling water, 
and made alkaline by the addition of the ammonia, is then 
poured into the mill and the leather is drummed for 15 min- 
utes. The chrome leather black dissolved in 4 gallons of 
boiling water is next added to the liquor in the drum through 
the trunnion, and the leather is drummed 15 minutes longer. 

2. Dyeing with logwood, leather black and titanium salt. 
— A rich black is 1 obtained by carrying out the following in- 
structions, the quantities of dyestuffs mentioned being suf- 
ficient for 100 lb. of leather: Drum the leather in a solution 
of 3 oz. of titanium-potassium oxalate for 10 minutes. Dis- 
solve, by boiling in 8 gallons of water, H lb. of logwood 
crystals, 4 lb. of chrome leather black, and 4 oz. of sal-soda, 
and drum the leather in this liquor for 15 minutes. Then 
pour in another solution of 3 oz. of the titanium salt and con- 
tinue drumming 10 minutes longer. The leather is then fat- 
liquored. 

3. Dyeing with acid-blacks. — This method of blacking the 
leather is preferable if the skins have not been entirely neu- 
tralized or if special value is placed on good penetration. 
From 1| to 2 lb. of nerazine G or of neutral black B are 
required for 100 lb. of leather. The leather is run for a few 
minutes with 10 gallons of water at 130° F. The dissolved 
dyestuff is then poured into the drum, and the drumming is 
continued for 20 minutes. About 1 lb. of formic acid is then 



390 PRACTICAL TANNING 

added and the drum is run for 10 minutes longer. For filling 
the leather, a fairly large quantity of logwood extract or gam- 
bier may be added to the dye-bath. When this method of 
dyeing is used, it is best to fat-liquor before dyeing, since the 
black is likely to bleed when an alkaline fat-liquor is used 
subsequent to the dyeing. 

Acid blacks are also combined with direct blacks to get 
good penetration; in this case, the addition of acid is omitted, 
the leather being entirely neutralized before it is blacked. 

Coloring chrome-tanned calfskins. — When these skins 
are to be colored, they should be selected with care. Only perr 
fectly sound skins free from lime spots, scars, and other 
defects, should be used. It is essential that the chrome tan- 
nage yields a full leather which is soft after it is dried, even 
if but lightly fat-liquored. Before any attempt at coloring is 
made, the leather should be thoroughly neutralized and washed 
free of acid and salts acquired during the tannage ; and after 
the skins have been washed it is necessary that they be shaved 
and made smooth and clean on the flesh side. 

Dyeing may be done in several different ways. The same 
procedure as given under dyeing sheepskins may be applied. 
The amount of color used will, of course, depend upon the 
depth of shade desired. 

In dyeing with basic colors, the stock is mordanted with 
sumac, gambier or fustic, and fixed with titanium-potassium 
oxalate. A solution of the basic dyestuff is then applied. 
Acid colors are used on chrome-tanned calfskins in the same 
manner as given under chrome-tanned sheepskins. For bright 
shades possessing good penetration a combination of acid and 
basic color is sometimes employed. 

Usually a drum is used so that a large number of the skins 
may be colored at one time, thus saving a great deal of time 
and labor. 

Dyeing vegetable-tanned calfskins black: Logwood 
liquor. — For blacking leather, logwood extract in paste, solid, 
and liquid forms are employed. 



DYEING LEATHER 391 

When the paste is used, from 6 to 8 lb. for each 100 lb. 
shaved weight is dissolved in 40 gallons of water together 
with | lb. of borax or sal-soda, and brought to boiling point. 
This liquor is very strong, and is usually diluted with water. 

Hematin and other similar products are used in the pro- 
portion of about 3 lb. for each 100 lb. shaved weight to a 
barrel of water. The dye is first boiled a few minutes in a 
half barrel of water, which is then filled with water. From 
1 to 2 lb. of borax may be added to the dye liquor. A few 
ounces of fustic paste or crystals boiled with the logwood 
serves to intensify the color. 

The leather is first given the logwood liquor by running 
in the drum for 20 minutes, and then the striker, consisting 
of a solution of 1 per cent of iron sulphate and \ per cent of 
copper sulphate, is introduced and the stock run for 15 min- 
utes longer. 

To color vegetable-tanned calfskins a deep black, the use 
of titanium-potassium oxalate as a striker is recommended, 
100 lb. of dry leather requiring from 8 to 10 oz. of the titan- 
ium salt. If the leather is not fat-liquored before dyeing, 
it should be washed, fat-liquored, dried, and finished. 

Dyeing with direct leather blacks. — Methods of dyeing 
leather black by the application of special blacks, without the 
use of logwood, are of fairly recent origin. Leather black 
T B and T G are useful in blacking any kind of vegetable- 
tanned leather, either on the grain side only, or upon both 
the flesh side and grain. The color is a rich, permanent black. 
The dyestufls are dissolved by mixing 2 parts by weight with 
1 part by weight of acetic acid (30 per cent), and then pouring 
boiling water over it while stirring constantly, so that a solu- 
tion of about 1 per cent results, which is diluted if necessary. 
The dyestuffs are applied in the customary manner, either by 
the staining process, or in a paddle or a drum. 

Coloring vegetable-tanned calfskins. — For this treatment, 
basic and acid dyestuffs are used. The latter are applied with 
the addition of some acid, 4 parts of an acid color usually 



392 PRACTICAL TANNING 

requiring 2 parts by weight of formic acid, or 3 parts by 
weight of lactic acid. The acid, before it is given to the 
leather, should be diluted with 100 times its weight of water. 
The leather is first run in a drum with the solution of dye- 
stuff, and when it has taken up most of the color, say in about 
15 minutes, the acid is poured into the drum and the leather 
is run for 10 minutes longer. 

The leather is frequently freshened up with sumac before 
it is colored. When this is done, it is likely to contain uncom- 
bined tannin, which causes uneven or cloudy coloring, so 
tartar emetic is used to prevent this. The leather is first 
drummed with sumac liquor. This may consist of a decoc- 
tion of sumac leaves or powder, or of a solution of 1 lb. of 
extract of sumac in sufficient water at 100° F. for 4 dozen 
skins. The leather is drummed with the sumac for 20 min- 
utes, after which, 8 oz. of tartar emetic, dissolved in water, 
is poured in, and the leather is run 20 minutes longer. The 
grain is thus cleared and prepared for the basic dye. No 
potassium dichromate or other setting agent is required, as 
the color will be fixed on the leather. 

In the treatment of leather which has acquired a dark color 
from the tannage it is advantageous to bleach it before 
coloring. 

In dyeing vegetable-tanned calfskins the same methods are 
employed as under vegetable-tanned sheepskins. The quantity 
of dyestuff used depends upon the depth of shade desired. 
As vegetable-tanned calfskins should be dried out before color- 
ing it is customary to run them in an emulsion of turkey red 
oil prior to dyeing. They may then be shaved, dampened 
back, and colored with basic, acid, direct, or alizarine dyes. 

Coloring velvet or suede leathers. — Coloring is done most 
satisfactorily with acid dyestuffs. The dye-bath is prepared 
in the usual manner, and \ lb. of potato starch is added for 
100 lb. of leather to ensure evenness of color and cover im- 
perfections. At the end of 20 minutes in the dye-bath, acid- 
ulate with £ per cent of sulphuric acid, rinse the dyed leather, 
set it out, and dry in the usual manner. 



DYEING LEATHER 393 

Finishing is done as follows : Dampen the skins with clear 
damp sawdust and stake; then buff them on the buffing ma- 
chine and fluff lightly on the flesh. In place of buffing on 
the wheel, the skins may be lightly worked over with the 
knife by hand, finishing off by working over the grain with 
a very fine emery made up into a suitable pad. The latter 
method gives an even, velvety feel and appearance to the 
leather. The finishing touch is a brushing with a stiff brush. 
For vegetable-tanned goods, which are to be stained on the 
flesh only, the buffing in the first stage applies, and when 
buffed, they can be treated as follows: First give the skins 
a coat of "clearing," made by dissolving 2 oz. of oxalic acid 
in 3 or 4 gallons of water. Allow them to level well by 
lightly airing, and then work over with a light coat of stain, 
using in the dyestuff solution 4 oz. of dextrine and 4 oz. of 
gum dragon in 8 to 10 gallons of solution. In staining this 
class of goods it is the rule to give first a weak coat to ensure 
a more even absorption of coloring matter, finally working 
up the shade required in the second coat. For producing 
good shades in light browns, the use of titanium-potassium 
oxalate will serve a useful purpose in obtaining a bottom 
which is really rich, using about 3 oz. of the salt to 100 lb. 
of leather, drumming the skins with the solution for 20 min- 
utes, and then adding the color solution to the drum. 

A light crutching and rubbing up the velvet on the colored 
side with a fine emery pad, or a light buffing on the wheel, 
finishes the leather. Coloring the skins according to the fol- 
lowing method produces deep penetration of color: The 
leather is buffed dry and soaked. It is then dyed warm in 
the drum with acid colors, some ammonia being added at the 
beginning of this operation. According to the thickness of 
the leather, up to 5 per cent of dyestuff, calculated on the 
weight of the moist leather, is used. The skins are dyed for 
one hour, the sulphuric or formic acid, up to £ per cent, being 
added towards the end of the operation. The leather is then 
rinsed thoroughly, set out, oiled, dried, and finished in the 



394 PRACTICAL TANNING 

usual manner by moistening in damp sawdust, drumming in 
a dry drum and glazing or ironing on the grain side. 

Black is produced by dyeing with 2 per cent of nerazine 
G, shaded if necessary with other dyestuffs, the acid being 
added after about an hour's dyeing, and the leather topped 
with 1 per cent of velvet black and some alum or acetic acid. 
It is then dyed 20 minutes, rinsed, set out, oiled, dried, and 
finished. 

Notes on ooze calf and Russia chrome leathers. — 
Chrome-tanned calfskins are finished into several fancy 
leathers. The most important of these are the boarded-tan 
calf, chrome Russias, and ooze in black and colors. The 
skins for boarded-tan calf and chrome Russia are selected in 
the wet tanned condition and colored before they are dried 
out. 

The skins for ooze leather are fat-liquored after tanning 
with an emulsion of egg-yolk and flour, and then dried; after 
which process they are sorted and colored. The fancy ooze 
colors according to the "Leather Manufacturer," can be made 
by bottoming with sumac or fustic extract and some mordant 
like sulphate of iron, tartar emetic, or titanium-potassium 
oxalate, then coloring with basic dyes; or by coloring with 
acid or diamine dyes, and sometimes topping with basic dyes. 
Some light shades are also made with pigments. 

Black ooze is made with a combination of logwood, nera- 
zine, or oxydiamine black and leather black, or with a com- 
bination of developed black and leather black. One process 
of making black ooze calf is as follows : The skins are sorted 
after washing out of the chrome tannage. They are next 
shaved and fat-liquored 30 minutes with 5 per cent egg-yolk 
and 10 per cent flour. The skins are then drained off, hung 
up, and dried. When dry, they are dampened in sawdust, 
staked, and buffed. They are then ready for dyeing. The 
skins must be buffed very clean so that after coloring they 
will not need a second burring. The next operation is a 
thorough wetting in a drum with water at 140° F. The 



DYEING LEATHER 395 

skins are next dyed 30 minutes at 130° F. with 12^ per cent 
diamine ooze black C R, then fixed 15 minutes with 5 per 
cent muriatic acid. The skins are next drained off and rinsed 
in cold water. They are then diazotized, running the first 
5 minutes in 10 per cent muriatic acid; then add 5 per cent 
sodium nitrite, and run them 15 minutes, drain them off, and 
wash thoroughly. 

The muriatic acid is given before the sodium nitrite be- 
cause the latter has an alkaline reaction, which has a tendency 
to wash the black from the leather before it can be diazotized. 
The diazotizing must be done cold so that the nitrous gas 
will not escape easily from the solution. 

The skins are now developed 15 minutes with 0.8 per cent 
phenylene-diamine dissolved with 1.6 per cent soda ash and 
0.2 per cent betanaphthol dissolved with 0.2 per cent caustic 
soda. The two solutions are made separately, but are mixed 
before they are applied. The skins are then drained off and 
washed, and next topped with 2 per cent leather black and 4 
per cent acetic acid. The skins are then thoroughly rinsed 
off and fat-liquored 45 minutes with 2 per cent of soluble oil. 
They are then dried on hooks, dampened in sawdust, staked, 
dry-milled, and tacked out. 

Chrome Russia leather and tan chrome boarded calf are 
colored in about the same manner. As the latter leather is 
glazed it is necessary to keep the colors lighter and yellower 
because the glazing makes them sadder and redder. These 
colors are usually made with basic dyes on top of a vegetable 
bottom, because they give very full, even shades. Acid and 
diamine colors which would be much faster to light can be 
selected. 

Dyeing chrome-tanned goat-skins: Dyeing with acid 
colors. — The neutralized and shaved leather is fat-liquored 
and then rinsed in water at 120° F. Twelve gallons of water 
heated to 125° F. is used in preparing the dye-bath for 100 
lb. of leather. The leather and the hot water are put into 
the drum. The solution of dyestuff without any addition 



396 PRACTICAL TANNING 

of acid is then poured into the drum while it is rotating and 
the leather is run for 20 minutes. If particular value is 
attached to a good penetration, 1 oz. or more of ammonia 
should be added to the dyestuff, but this is effective only where 
the skins have been completely neutralized. 

At the end of the 20 minutes, the dye-bath is acidified by 
adding formic or sulphuric acid, preferably the former. 
Enough acid should be used to neutralize the ammonia, and 
in addition, 2 parts by weight of formic acid or 1 part by 
weight of sulphuric acid for every 4 parts by weight of dye- 
stuff are necessary. After the color-bath has been thus acidi- 
fied, the leather should be drummed 10 minutes to allow the 
dyestuff to become fixed. 

The addition of some sumac or gambier liquor to the dye- 
bath after it has been acidulated improves the feel and full- 
ness of the leather, and makes it easier later on to obtain a 
good glazed finish. 

To remove any excess of acid which may be present in the 
leather after it has been colored, a solution of 4 oz. of sodium 
acetate crystals for each 100 lb. of leather should be added to 
the water in which the skins are rinsed. 

Very full shades are obtained by first coloring with acid 
dyes and then topping with basic color. This is done by add- 
ing a solution of some basic color — -2 oz. or more of dyestuff 
for 100 lb. of leather — as soon as by the addition of acid all 
of the acid color has been exhausted from the dye-bath. If 
this cannot he effected completely, the topping may be carried 
out in a fresh bath, in which case no further rinsing is needed. 

The temperature of the dye-bath should be kept as high as 
possible during the process, not lower than 120° F. It is 
advisable to pass the skins through hot water before throwing 
them into the drum, or treat them in it to warm them thor- 
oughly. The sumac liquor used with the solution of dye- 
stuff is made by steeping from 12 to 16 lb. of sumac leaves, 
sumac powder, or sumac extract, in 10 gallons of hot water; 
2 gallons of the decoction is used for 100 lb. of skins. Sumac 



DYEING LEATHER 397 

may, however, be partly or wholly substituted by gambier; 
that is to say, the liquor may be made of equal parts of sumac 
and gambier, or gambier may be used alone. 

Dyeing with basic colors. — The method of coloring chrome 
leather with basic dyes generally used consists of mordanting 
it with tanning extract such as sumac, gambier, or combina- 
tions of these two; or gambier and fustic, the latter or osage 
orange also being often used alone. Dyeing may be done 
either before or after the skins have been fat-liquored. For 
the mordant, sumac is chiefly used for light shades, fustic 
or osage orange for tan and yellow shades, and gambier for 
the darker ones. A decoction of 4 to 5 lb. of sumac is suffi- 
cient for 100 lb. of leather. After having been treated with 
sumac, gambier, fustic or osage orange, the skins are dyed 
with basic colors. The dyeing period should last 15 or 20 
minutes, and the temperature of the bath should be 125°. It 
is advisable to add the dyestuff to the leather in several por- 
tions through the hollow axle while the drum is rotating. The 
drum should not be stopped until the solution of color has 
been in at least 10 minutes, otherwise the leather may be 
spotted. 

Sumac mordant for basic and acid dyes. — Chrome-tanned 
goatskins are nicely colored by carrying out the following 
instructions : Prepare a sumac liquor by using a decoction of 
4 to 6 lb. of sumac leaves for 100 lb. of skins, or a solu- 
tion of 20 oz. of extract of sumac; use at a temperature of 
125° F., and drum the leather in it for 20 minutes. Then 
pour in 4 oz. of titanium-potassium oxalate dissolved in a 
little hot water for 100 lb. of leather, and let the drum rotate 
10 minutes longer. Then drain the liquor out of the drum 
and run the skins in a solution of dyestuff, either basic or 
acid dyes being used, preferably the latter. The result of 
this method of coloring gives full and uniform shades of 
color. It is also good practice to apply the dyes first to the 
sumac-treated skins and the titanium salt afterwards. This 
gives clear, bright colors. 



398 PRACTICAL TANNING 

Gambler mordant for tan shades. — For 100 lb. of stock, 
use 2 lb. of gambier dissolved in 12 gallons of water at a 
temperature of 125° F. Drum the skins in this solution for 
20 minutes. Then pour in 3 or 4 oz. of titanium-potassium 
oxalate dissolved in hot water, and let the drum turn 10 min- 
utes longer. Drain out the liquor and color the leather with 
acid dye, or rinse it in warm water and color with basic 
dyestuff. 

A liquor composed of equal parts of gambier and fustic is 
also an excellent mordant for shades of tan and brown. 

Process for tan and brown shades. — Drum the leather for 
10 minutes in a solution of 3 oz. of titanium-potassium oxa- 
late; add 1 lb. of fustic crystals dissolved in boiling water 
and drum 10 minutes; pour in another solution of 3 oz. of 
titanium salt and drum the leather 10 minutes longer; wash 
the skins, drain, and dye them with phosphines shaded with 
Bismarck brown to the exact color desired ; drum 20 minutes, 
then fat-liquor the leather — if not fat-liquored before dye- 
ing — with a slightly alkaline fat-liquor, and finish as usual. 
Five ounces of liquid extract of fustic may be used for each 
dozen skins, or 1 to 2 lb. for 100 pounds. 

Clearing the grain of grease. — Skins which have greasy 
grain may be cleared by being drummed 15 minutes in a solu- 
tion of 1 to 2 gallons of lactic acid in 50 gallons of hot water; 
they are then rinsed and treated with sumac, gambier or fustic, 
and colored. The acid removes the surface grease and opens 
up the pores of the grain so that the mordant and dye may 
go in more deeply and more uniformly. 

Dyeing with fustic extract and direct or anthracene colors. 
— Wood dyes, such as fustic extract, may be used with direct, 
or anthracene colors in the production of fast colors on chrome 
leather. The process is as follows : The leather is drummed 
for 30 minutes with the requisite quantity of fustic extract. 
The solution of dyestuff is then poured in and the drumming 
is continued for a half-hour longer. Complete absorption of 
the dyestuff is finally brought about by the addition of 2 or 3 
oz. of acetic acid per 100 lb. of leather. 



DYEING LEATHER 399 

Color of superior fastness may be obtained by adding from 
4 to 8 oz. of sodium dichromate to the color-bath before the 
acetic acid is added, and by working the goods at as high a 
temperature as possible, or from 150 to 160° F. The liquor 
is then drained out of the drum and the leather is topped in 
a fresh bath with basic dyestuff. The leather is fat-liquored 
either before the dyeing is begun or after topping with basic 
color. In the latter case it should be rinsed thoroughly be- 
fore it is fat-liquored. 

Light shades, such as gray, drab, champagne, beige, bis- 
cuit, etc., are obtained by using acid dyestuffs in the follow- 
ing manner: The neutralized leather is drummed with the 
diluted solution of dye (3 to 4 oz. for 100 lb. of leather) 
at a temperature of 130° F., for 10-minutes. The fat-liquor 
is then poured in and the leather is drummed for a half-hour. 
This method of working may be reversed by commencing with 
the fat-liquor and adding the dyestuff after some time, also 
by using both dyestuff and fat-liquor simultaneously. All 
that is needed to obtain complete penetration is to neutralize 
the leather completely and prolong the drumming correspond- 
ingly. If necessary, -J to 1 per cent soap may be added to the 
ordinary fat-liquor. It is usually advisable to add a decoc- 
tion of from 6 to 8 lb. of sumac or a solution of 3 to 4 lb. of 
gambier to the bath after the fat-liquor has been exhausted 
by the leather, and allow the drum to rotate a half -hour 
longer. The leather is then rinsed and set out. 

Use of tartar emetic. — Chrome-tanned leather, previous to 
the application of artificial dye, is usually prepared with some 
tanning extract, as already stated. When uncombined tannin 
remains on the grain of the leather imperfect coloring results, 
and to prevent such defect and fix the color on the leather 
some dyers use tartar emetic, which is a tartrate of antimony 
and potassium. The leather is run in the sumac, gambier, 
or fustic liquor, as the case may be, the required period, when 
tartar emetic dissolved in hot water is added to the drum and 
the leather is drummed 15 minutes longer. At the end of this 



400 PRACTICAL TANNING 

time it is rinsed in warm water and colored with basic dye, 
then rinsed again and fat-liquored. Two ounces of tartar 
emetic is generally sufficient for one dozen skins. 

Notes and suggestions. — While fustic extract is used in 
coloring, it may be combined with the fat-liquor, and the two 
processes of mordanting and fat-liquoring performed at one 
operation, coloring being done afterwards. 

When chrome-tanned skins are colored after they have been 
fat-liquored, more dye is required than when coloring is done 
previous to fat-liquoring. This is due to the fact that the 
fat-liquor prevents penetration of the dyes into the pores of 
the leather. On the other hand, when the leather is colored 
before it is fat-liquored, the hot fat-liquor removes much of 
the color and makes it difficult to get the exact shade wanted. 
Basic dyes have the advantage over acid dyes in that no acid 
is required to set the color. When acid dyes are used, the 
leather should be washed and freed from every trace of acid 
before it is fat-liquored. It .is the custom to color and fat- 
liquor chrome leather before drying it out, as it is not prac- 
ticable to color the leather by the usual methods after it has 
been dried. It is said, however, that the leather can be fat- 
liquored and dried, and then wet-back and colored with acid 
dyestuffs in a bath to which a quantity of sodium bisulphate 
has been added. The process is as follows : The acid dye 
is dissolved in boiling water. Bisulphate, equal to the amount 
of dye, is dissolved in hot water in a separate vessel. Half 
of the dye solution and all of the soda solution are added to 
enough hot water to drum the leather — 12 gallons for 100 lb. 
of leather — the skins being drummed in the liquor for 15 
minutes. The remainder of the dye is then added, the leather 
is drummed 30 minutes longer, then washed in warm water, 
set out, and dried. From 8 to 10 oz. of dyestuff is usually 
required for a dozen skins. This method of dyeing is said 
to color leather satisfactorily which has been dried after fat- 
liquoring. 

It has been found that a better finish can be secured on 



DYEING LEATHER 401 

skins that have been given a light re-tannage with some vege- 
table tanning extract, either before or during the coloring 
process. Acid dyes are used successfully on such a bottom. 
A mixture of 2 per cent of fustic extract and £ per cent log- 
wood crystals produces excellent results as a mordant. After 
having been colored with coal-tar dye on this bottom, the 
skins are drained, and treated with an acid fat-liquor or an 
emulsion of oil and egg-yolk. Some dyers use basic color on 
top of an acid color, which makes the color faster to the fat- 
liquor. Applying fustic and logwood first, then acid dyestuff, 
and topping with basic dye, is a good method of obtaining 
tan and golden-brown shades. Sulphuric or formic acid added 
towards the end of the process increases the depth of color. 
Formic acid is preferable to sulphuric acid, as the latter is 
liable to cause greasy spots by curdling the fat-liquor. 

Coloring with natural dyestuffs. — A few practical instruc- 
tions will now be given by means of which chrome-tanned 
goatskins can be colored desirable shades without the use of 
artificial dyes. Fast colors are obtained by using dyewood 
extracts, and the cost of the materials is less than that of 
coal-tar dyes. 

Light tan shade. — Take the shaved skins and put them in 
the drum with 12 gallons of water heated to 125° F. In a 
clean pail, dissolve 2 lb. of fustic extract (lemon shade) in 
hot water. Start the drum, and then add the solution of fustic 
and run the skins in it for a half -hour. Then add 4 oz. of ti- 
tanium-potassium oxalate dissolved in a little hot water, and 
let the drum run 15 minutes longer. The skins will then be 
found well colored, and should be washed and fat-liquored. 
The color, if not quite satisfactory, can be modified by the 
use of coal-tar dye. 

Dark tan shade. — Run the skins in a solution of 4 lb. of 
fustic extract (red shade), at a temperature of 125° F., for 
30 minutes, using 12 gallons of water for 100 lb. of leather. 
After that period, add without stopping the drum, 6 oz. of ti- 
tanium-potassium oxalate dissolved in a little hot water. Allow 
the drum to turn 15 minutes longer, then wash and fat-liquor. 



402 PRACTICAL TANNING 

Ox-blood shade. — A desirable shade of ox-blood is produced 
in the following manner: For 100 lb. of leather, dissolve 
2\ lb. of hypernic extract, 2 oz. of logwood extract, and \ 
oz. of leather red by boiling in a few gallons of water; then 
add sufficient water to make 12 gallons of liquor, and use it 
at 125° F. Drum the skins in this liquor for 30 minutes. 
Then dissolve and add 4^ oz. of titanium-potassium oxalate 
and allow the drum to rotate 15 minutes longer. The skins 
are then in condition to be washed and fat-liquored. 

Chocolate shade. — For this color use 2\ lb. of fustic ex- 
tract (lemon shade), 10 oz. of hypernic extract, and 3 oz. of 
logwood crystals in 12 gallons of water for 100 lb. of skins. 
After the drum has been running 30 minutes, pour in 5 oz. of 
titanium-potassium oxalate dissolved in hot water. Run the 
drum 15 minutes longer, then wash and fat-liquor the skins. 

Dyeing chrome-tanned goatskins black. — These skins 
may be dyed black in a variety of ways. The customary 
method is to dye them in a drum, using logwood extract and 
direct leather blacks, thus obtaining a full black in one opera- 
tion, and fat-liquor them after they have been blacked. The 
skins should be thoroughly neutralized and shaved before they 
are dyed. 

Dyeing with hematin crystals or logwood and direct leather 
black. — This is one of the most approved methods of blacking 
chrome leather. The pack of skins (100 lb.), is weighed and 
thrown into the drum with 12 gallons of water heated to 125° 
F. Dissolve 1 lb. of hematin or logwood crystals in boiling 
water and add a little ammonia. The liquor is poured into 
the drum through the hollow axle and the leather is drummed 
15 minutes. Dissolve 1^ lb. of direct chrome leather black 
C in boiling water and add the solution to the drum, and run 
the leather 15 minutes longer. The exhausted dye liquor is 
then drained out and the hot fat-liquor is poured in. After 
is has been fat-liquored, the leather is washed 5 minutes in 
warm water, set out, oiled, and hung up to dry. 

Dyeing zvith logwood, leather black, and titanium-potas- 



DYEING LEATHER 403 

siimi oxalate. — For 100 lb. of leather a solution of 3 oz. of 
oxalate is used, and the leather drummed in it for 10 min- 
utes. A solution of 1^ lb. of logwood crystals, | lb. of 
chrome leather black, and 4 oz. of sal-soda in boiling water, is 
next added and the leather is drummed for 15 minutes. Then 
a solution of 3 oz. of oxalate is added to the drum, and the 
treatment is continued 10 minutes longer. The leather is then 
either washed, struck out and fat-liquored, or fat-liquored 
immediately after it is blacked, and washed afterwards. 

Dyeing with chrome leather black. — The skins, neutralized 
and shaved, are fat-liquored and then thrown into the drum 
for blacking. A solution of 1| or 2 lb. of chrome leather 
black C in 10 gallons of water is poured into the drum, and 
the leather is treated with it for 30 minutes. The tempera- 
ture at the beginning of the process should be 125° F. To 
fix the dyestuff, 1 oz. of acetic acid may be added towards the 
end, but in most cases this is unnecessary. A black grain 
and a blue-black flesh are obtained when this method is em- 
ployed. Logwood extract or crystals may be used with the 
direct black to increase the fullness of the leather. The log- 
wood solution may be added along with the dyestuff or im- 
mediately afterwards. No striker or other medium is 
required, the logwood becoming fixed on the leather during 
the dyeing. 

'Another method of direct blacking. — The following proc- 
ess can be used if the flesh side is to be dark blue or blackish- 
blue. The leather is first dyed for 20 minutes at 125° F. in 
the drum with 6 to 12 oz. of chrome leather black C in 10 
gallons of water; then f oz. of acetic acid is added for fix- 
ing the color, and 10 minutes later 6 to 9 oz. of leather black 
T B or T G. The leather is drummed 10 minutes longer and 
then rinsed. Fat-liquoring may be done either before or 
after blacking. 

Blacking with logwood and iron liquor. — For 100 lb. of 
leather, boil 3 lb. of logwood extract and 4 oz. of fustic ex- 
tract, in 12 gallons of water, and add 1 oz. of ammonia. Drum 



404 PRACTICAL TANNING 

the skins 30 minutes, then drain off three-fourths of the dye 
liquor and pour in, after the drum is turning again, 4 or 5 
oz. of iron liquor in 10 gallons of water. After a further 
drumming for 10 minutes, the liquor is drained off and the 
skins washed thoroughly in running water. 

Dyeing with logwood, potassium permanganate, and iron 
liquor. — This process is used in the following manner : In 
the drum are placed 450 lb. of skins as they come from the 
shaving machine, and 30 gallons of water heated to 120° F., 
after which the drum is closed and started. Dissolve 2\ 
lb. of permanganate in 55 gallons of water at 120 F., and add 
2\ lb. of muriatic acid of 21° Be., this solution being run into 
the drum through the hollow gudgeon. After 10 minutes, 
stop the drum, open it, and allow the liquor, which is now 
spent, to run out. Close the drum again, and after re-start- 
ing, pour 2 gallons of iron liquor mixed with 45 gallons of 
warm water in through the hollow axle. After 10 minutes, 
stop the drum, and allow the liquor to drain out. Next dis- 
solve 3 lb. of extract of logwood and 3 lb. of sal-soda in 45 
gallons of warm water, and after the drum has been started 
again, add this liquor through the gudgeon. Allow the drum 
to run 10 minutes, then stop it, and remove the skins. The 
next step is washing the leather, which is now black; this is 
done in a drum or twister supplied with running water. After 
being washed 15 minutes, the leather is ready to be fat-liq- 
uored and dried for finishing. 

The iron-liquor referred to can be purchased as black iron, 
or may be prepared by dissolving scrap iron in dilute com- 
mercial acetic acid. The liquor ready for use should stand 
at 10° Be. ; but any suitable ferrous salt of iron may be 
substituted. 

The muriatic acid should always be added to the perman- 
ganate solution when all of the water required is present, 
and never to a hot concentrated solution of permanganate. 
It is claimed that a deep, rich, and more permanent black, be- 
sides other advantages, is economically obtained by using this 



DYEING LEATHER 405 

process, which was patented by William M. Norris, Princeton, 
New Jersey. 

Dyeing chrome kangaroo black. — The same methods as 
given under goatskins may be applied to this class of leather. 

Yellow flesh and black grain. — Where leather with a yel- 
low back and black grain is required, the skins are treated 
with acid fat-liquor after they are tanned, and are then dried. 
Preparatory to flesh coloring, the leather is wetted in a tub 
of warm water and placed in a pile to soften. For 100 small 
and medium skins, | pail of sumac is scalded with hot water 
for 2 hours. The sumac, with 4 pails of water, made slightly 
acid with lactic acid, is put into a drum and milled 25 min- 
utes, the temperature of the liquor being 110° F. After the 
skins have been drummed in the sumac liquor, the yellow 
dye is added, and the leather run in it for 10 minutes. For 
the dye, dissolve 1 lb. of yellow S or other basic yellow in ^ 
barrel of water, and use 3 or 4 pails of the solution for 100 
lb. (dry weight) of leather. 

After the leather has been colored yellow, dye the grain 
on a table or a machine with logwood and striker, or with a 
solution of direct leather black. Rinse the leather, set out the 
grain, oil it lightly, then hang up the skins to dry. 

Chrome-tanned ooze calfskins. — The skins that are 
worked into ooze leather must be free from butcher cuts 
and have full flanks, but good grain is not essential. In 
almost every pack of skins there are some that have defective 
grain which are unsuitable for grain finish, and can be fin- 
ished only upon the flesh side. Such skins can be sorted out 
after the pack has been tanned, or they can be selected after 
they have been de-haired, and tanned separately from the 
others. 

One method of finishing the skins into ooze leather is as 
follows : The skins are treated with a suitable fat-liquor, and 
some substance is added to the same, which, during the sub- 
sequent drying, isolates the fibers of the leather in such a 
manner as to allow them to be soaked and softened without 
difficulty. For this purpose, dextrine, grape sugar, syrup, 



406 PRACTICAL TANNING 

etc., are used. The stuffed leather is dried and then buffed. 
Buffing is done either by running the flesh-side on an emery 
wheel or by slightly snuffing the grain. The snuffed leather 
is then drummed with warm water until it has regained its 
original softness, and is then colored with acid dyestuffs. 
During or after dyeing a somewhat larger quantity of gambier 
or sumac is added than is otherwise customary with chrome 
leather, in order to impart the necessary firmness to the 
leather. The nap of the skins is then raised by working the 
leather in a dry drum after it has absorbed some moisture 
by a treatment with wet sawdust. The coloring is done in 
the same manner as described for grain leather. 

Another way to produce ooze leather is as follows : After 
shaving, 100 lb. of skins are run with 1 quart of pumice in a 
clean drum for 30 minutes ; then the flesh side is cut on a wet 
wheel so that the fibers are uniformly fine over the entire 
skin. After this has been done, wash the leather thoroughly 
to remove all of the pumice. The skins are then in condi- 
tion to be colored and fat-liquored, these processes being the 
same as for grain-finished leather. 

If black leather is desired, drum the skins in a solution of 
Bismarck yellow-brown or some other direct yellow-brown, 
then drum with a logwood liquor which is slightly alkaline, 
and strike with acetate of iron or copperas (iron sulphate), 
and fat-liquor them, following this with direct leather black, 
fat-liquoring again, and then hanging the skins up to dry. 

There are special ooze blacks on the market which produce 
good results. They dye direct without the use of a mordant 
or logwood. 

For light skins, a fat-liquor of egg-yolk and sperm oil is 
suitable; and for both light and heavy skins, one made of 
olive-oil soap, neat's foot oil, and moellon degras is recom- 
mended. It is made as follows : 1 lb. of the soap is dissolved 
in 6 gallons of boiling water. To the solution is added 4 
lb. of the oil and 2 lb. of degras, and the whole is boiled for 
30 minutes. Next add water to make 20 gallons of liquor. 



DYEING LEATHER 407 

In a separate vessel dissolve 6 oz. of potassium carbonate, add 
this to the fat-liquor, and stir thoroughly. This quantity of 
fat-liquor is sufficient for 200 lb. of leather. Use it at 140° 
F. Drum the leather 40 minutes, and then let it drain until 
the next day. Strike out each skin ; oil the grain lightly, and 
hang up to dry. 

When dry, dampen and stake the skins, and before they 
are dry, put them into a dry wheel and run them 3 hours; 
then tack them out. When dry, stake them lightly and run the 
flesh side on a plush wheel, which is the finishing touch. 
Softness, freedom from spots, and smooth, uniform colors 
and fibers are the essential qualities of this leather. 

Velvet or suede leather is finished from chrome calfskins in 
the following manner: The skins are taken in a dry or crust 
condition and are dampened with clean, wet sawdust in the 
customary manner. They are next fluffed on the flesh side,' 
care being taken to avoid scratches with new or coarse car- 
borundum or emery. The grain then receives a thorough 
grinding on the buffing-wheel, after the leather is perched or 
staked lightly. After buffing, the skins are given a coat of a 
solution of dextrine, potato starch, or Irish moss (kelp ex- 
tract), and are then allowed to remain until the moisture 
has almost evaporated from them. Sufficient moisture should 
be left in the goods to keep them cool for the wheeling or 
fluffing on the grain, which follows immediately. 

The next process is coloring ; and for this a good drumming 
in warm water is necessary to soften the leather. Add 8 oz. 
of borax to 12 gallons of water, and drum the skins 20 min- 
utes ; then rinse them for a few minutes. 

A. treatment with sumac is necessary to impart firmness 
to the leather, 3 or 4 lb. of sumac extract in water at 125° 
F. being used for 100 lb. of leather, which is drummed 30 
minutes. A solution of gambier is also suitable for the pur- 
pose. Drain the liquor out of the drum and proceed to color 
the leather with acid dyes. Prepare the dye-bath by dis- 
solving the amount of color necessary in 15 gallons of hot 



408 PRACTICAL TANNING 

water, pour this solution into the drum while it is rotating, 
and run the skins 10 minutes. Then add 4 or 5 oz. of fustic 
extract (a tannin from a West Indian wood) in solution to 
the bath and let the drum run 20 minutes longer. Then acid- 
ulate the dye-bath by adding 3 or 4 oz. of sulphuric acid, or 
three times as much sodium bisulphate in 1 gallon of water, 
and let the drum run 15 minutes longer. The dyed leather is 
next rinsed well in lukewarm water, and then given a drum- 
ming with a solution of egg-yolk for 10 minutes; it is then 
rinsed, struck out, and dried. 

Complete penetration of the dye is secured by adding 2 
oz. of strong ammonia to the dye-bath, and prolonging the 
drumming to 40 minutes or even longer ; the ammonia is then 
neutralized by using slightly more acid or soda than the quan- 
tity mentioned. 

The finishing operations consist of dampening the dry skins 
and staking them, then buffing on the machine and fluffing 
lightly on the flesh side. In place of buffing, they can be 
worked over with a warm knife, and finished off by working 
over the grain with very fine emery made up into a suitable 
pad. This last method gives a beautiful, even, velvety feel, 
and fine appearance to the leather. The last touch is brush- 
ing with a stiff brush. 

Chrome bag and belt leathers. — Black chrome leather 
with a printed or boarded grain is used to some extent in 
the manufacture of hand bags and traveling bags, and belts 
for personal use. The leather, when it is suitably fat-liquored 
and finished, is well suited for these purposes, as it is soft, 
durable, and waterproof. It must, however, be firm, clean, 
and free from grease. The sides are tanned in the same man- 
ner as for shoe leather, preferably in the one-bath process, 
but the leather is given less fat-liquor. It is desirable that 
the color penetrate through the flesh so that the edges will 
be black and not blue. Direct blacks are preferable to log- 
wood for dyeing. The leather is fat-liquored and then dyed, 
or it may be run first in a solution of the dye to stain the 



DYEING LEATHER 409 

flesh, then fat-liquored and dyed on the grain by hand. The 
use of a direct chrome black with logwood produces a rich 
color, and gives a fuller feel to the leather than the direct 
black alone. It is also practicable to fat-liquor the leather 
while it is being dyed, drumming it first in the dye liquor and 
then with hot fat-liquor. The fat-liquor may be a solution of 
sulphonated oil or a mixture of such oil and neat's foot oil. 
Getting the leather too soft and greasy must be carefully 
watched as when it is greasy, the grease strikes through the 
linings and is easily perceptible, so the leather must be fat- 
liquored just enough to make it supple without being soft 
and stretchy. 

The grain is boarded two ways, or printed with a box grain 
arid then boarded. Belts made of this material are almost 
indestructible, and bags give great satisfaction as regards ap- 
pearance and wear. The more novel the leather is made to 
appear the more it is liked, there being an unceasing demand 
for new things in these lines of leather goods. 

Dyeing chrome side leather.— This is done quickest and 
most uniformly in a drum, the general practice. For 
the production of the shades of tan and brown usually in 
demand, acid and basic dye-stuffs are used. The acid colors 
may be applied direct to the chrome leather without a mor- 
dant, although most tanners prefer to bottom with fustic and 
titanium-potassium oxalate. The basic colors are always ap- 
plied upon a tannin mordant or base. 

Direct dyeing with acid colors. — The same method as given 
under goatskins may be applied to this grade of leather. 

Tannin mordant for basic dyestuffs. — Coloring with basic 
dyes is effected by first applying a mordant of gambier, fustic 
or sumac, fixing with titanium-potassium oxalate or tartar 
emetic, and then dyeing to the shade desired with the proper 
dye. 

Red-brozvn shade. — A popular shade of red-brown is ob- 
tained by applying 4 oz. of alizarine brown G, 4 oz. of alizar- 
ine yellow R extra, and 1 oz. of alizarine new yellow extra 



410 PRACTICAL TANNING 

for 100 lb. of leather. Dissolve the alizarine brown G by 
boiling in 8 gallons of water, then acid 4 gallons of cold water, 
and use the solution at 160° F. Drum the leather in this 
solution for 15 minutes. 

Meanwhile, dissolve the other dyes in 3 gallons of boiling 
water and pour into the drum. Let the drum run 15 minutes; 
then drain off the liquor and fat-liquor the leather. It is 
also beneficial to the color to add 1 lb. of extract of fustic dis- 
solved in hot water to the drum after the second 15 minutes, 
and let the drum run another similar period. Then dissolve 
and add 2 oz. of sodium dichromate, running the drum 10 
minutes longer. Wash and fat-liquor the leather. 

Dyeing chrome side leather black. — One of the most 
approved methods of dyeing chrome side leather black con- 
sists of the application of logwood and direct chrome leather 
black. The wet shaved leather is weighed and thrown into 
a drum with 12 gallons of water at 125° F. for 100 lb. of 
stock. Dissolve 1 lb. of hematin in water at 125° F. ; add 1 
oz. of ammonia to the solution, pour the latter into the ro- 
tating drum and run the leather for 15 minutes. Dissolve 1^ 
lb. of chrome leather black in water at 140° F., and pour 
the solution into the drum. The leather is treated 15 min- 
utes, and may then be drained and fat-liquored, or the fat- 
liquor can be added to the dye-bath at the end of the dyeing 
process, the drum being run a half-hour longer. The leather 
is then washed in warm water, set out, oiled with suitable 
oil, and hung up to dry. Other methods already described 
may be used equally well on side leather. 

Yellow leather. — If yellow leather is required, the stock may 
be colored with gambier in the following manner : Boil 125 
lb. of gambier in 20 gallons of water, add 1 pint of mu- 
riate of tin and 3 oz. of tin crystals, stir thoroughly, and fill 
the barrel with water. For 50 sides use 4 pails of this gam- 
bier liquor, and add 2 gallons of water, also ^ lb. of picric 
acid and -J lb. of fustic dissolved in 3 gallons of hot water. 
Mix the color solution in a tub and use it at 90° F. Drum 
the leather in it for an hour. 



DYEING LEATHER 411 

Coloring vegetable-tanned upper leather. — Hides that 
have been tanned by a gambier, quebracho, or combination 
process can be finished in various ways. For black upper 
leather — glazed or dull — the following process may be carried 
out: The grains of sides split out of lime, bated, pickled, and 
tanned, or the grains of sides split after tanning and then 
re-tanned, are washed and pressed. They are then fat-liquored 
and dried. The dry leather is then wet-down and colored blue 
or blue-black as a foundation for the subsequent black. The 
grain is next dyed black with logwood and striker, or with a 
direct leather black applied by brushing on. The skin is then 
set-out smooth and hung up to dry; next dampened, staked, 
and trimmed. 

Where colored leather is wanted, the leather is fat-liquored 
and dried; then treated with sumac and colored; or it may 
be fat-liquored after coloring, and then dried and finished. 

For both black and colored leather, the author would 
recommend the use of sulphonated oil fat-liquor. 

Where it is desired to dye only the grain black, leaving the 
flesh undyed, the use of direct blacks such as leather black 
T B and T G is preferred. For bright finish the bluish leather 
black T B is especially well suited ; for leather which is to be 
finished dull, the deeper and Somewhat more greenish leather 
black T G is preferable. Leather which is given a moderate 
polish by being rolled or brushed may be dyed equally well 
with either brand. No preparatory or after-treatment is 
required. 

Blacking the grain side only is done by brushing the solu- 
tion of dye into the grain, two coats being generally sufficient 
for the dry leather. The color solution consists of 1 lb. of 
the leather black and 8 oz. of acetic acid in 10 gallons of 
water, the temperature being maintained at 120 to 140° F., 
during the operation. The dye is mixed with the acid and 
enough boiling water is poured over the pulp to make a solu- 
tion of the proper strength. 

Dyeing sealskins. — The well set-out skins are placed in 
piles, one dozen in each, with the necks and butts running 



412 PRACTICAL TANNING 

one way, and are then dyed with the following materials : 

Blacking. — A pail of good strong logwood liquor, to which 
a half cup of ammonia has been added, is heated to boiling 
point and applied to the skins with a brush. This is imme- 
diately followed by a solution of iron liquor and glue, pre- 
pared by pouring 1 gallon of iron liquor over ^ lb. of best 
glue; this is allowed to stand a few hours and is heated be- 
fore use. This "floss," as it is commonly called, is put on 
the skins evenly and thinly, and rubbed in thoroughly. After 
blacking, the skins are laid face to face, covered up, and al- 
lowed to remain over night for the black to set. 

They are then grained from angle-to-angle with a board 
covered with a piece of thin tin, perforated similar to a nut- 
meg grater. After these two "cuts" they receive another cut 
on the belly with a cork-board, followed by a cut straight up 
the skin; they are dried in a hot room, "emeried," and 
seasoned. 

The goods may also be utilized for colors by soaking in 
warm water, running them through a weak acid-bath and 
dyeing in a paddle at 115° F. If acid dye is used, the goods 
can be dyed out of tan; if dyeing is effected with basic dye, 
the tannin should be fixed with tartar emetic. After dyeing 
to shade, wash in cold water and tack out, taking care that 
the goods are not dried too rapidly, a moderate heat being 
preferable. When dry, they are taken off the frames or boards, 
and the side that is to be faced is filled with a potato-flour 
paste, made by adding sufficient farina to water to form a 
stiff paste. When the paste is cold, add a little color and 
apply a good coat, after which tack on the frames. 

Dyeing pigskins. — Dry the leather and store it away for 
a while to mellow. Then, if it is to be colored, dampen and 
clean the grain with borax followed by sulphuric acid. To 
do this, wash the leather for 15 minutes in a warm solution 
of borax. Drain off the solution and run the skins in a solu- 
tion of sulphuric acid. Drum them in this solution, then wash 
and run them in sumac again. After having been rinsed they 
are in condition to be colored. When colored, give them a 



DYEING LEATHER 413 

light coat of cod oil and dry. Staking, boarding, and glazing 
complete the process. 

If black leather with undyed flesh is required, the skins 
should be dyed on the grain side only by the staining method. 
A solution of 1 lb. of leather black in 10 gallons of water 
is recommended for this purpose. It is brushed on the grain, 
two applications being usually sufficient. 

Pigskins are much used in plain russet finish. For this 
they need to be bleached according to the instructions given 
above. For inner-soling, the skins are oiled with a mixture 
of fish and mineral oils, and finished by rolling. 

Process for producing marbled suede leather. — The fol- 
lowing description covers a process of finishing the flesh side 
of leather so that it will have a mottled appearance and a 
velvety feel. Leather made in accordance with the directions 
given is soft and pliable and has a velvety surface, which is 
ornamental and adapted for use in making ladies' bags, for 
table covers, and for a great variety of articles for which a 
soft ornamented leather is desirable. 

The skins are tanned as usual, and the flesh side is then 
subjected to the customary preliminary steps taken in the 
ordinary manufacture of suede or velvet leather, that is, shav- 
ing and then wet-wheeling, or subjecting it to the action of an 
emery wheel while it is wet. While still wet, the skin is laid 
on a table with the flesh side up, and is puckered or gathered 
into folds, this being preferably done by hand, and some dye 
is poured onto the flesh side. 

The exposed portions of the skin will, of course, be ex- 
posed to the full action of the dye, while the portions within 
the folds or puckers will be more or less affected, depending 
upon the character of the fold. If the fold is a deep one, 
and the sides happen to be pressed closely together, the dye 
will not penetrate to any extent into the fold, and the surface 
of the leather within the fold will remain practically in its 
natural condition. Other portions of the skin, where the two 
sides of the fold are not pressed closely together, will be 
affected somewhat by the dye and will be partly covered, al- 



414 PRACTICAL TANNING 

though the color will not be so deep as at the parts entirely 
exposed. The skin is then buffed on fine emery, dried, and 
the flesh washed, which results in giving it the velvety sur- 
face desired. 

Pigment finish.* — Owing to the shortage of dyestuffs dur- 
ing the early part of the world war, tanners were forced to 
try other means for coloring leather, and somebody sug- 
gested the use of mineral pigments. The results were so 
satisfactory that the application of pigments at once became 
general. Even now that coal-tar colors are again available, 
many tanners prefer to continue using pigments. 

In the coloring and finishing of leather by means of pig- 
ments there are two general methods of application. The 
first is employed for coloring splits and ooze leather, and 
consists of adding the pigment in the mill ; while in the other 
method the pigment is applied by hand or machine after the 
leather has been mill-colored with artificial or natural dyestuffs. 

Mill coloring. — This method is mostly applied to splits. The 
neutralized, washed, and fat-liquored leather is pressed or 
whizzed to remove excess of water, and is then placed in 
the drying wheel and run in the presence of hot air until dry, 
and then sorted for coloring. The splits are placed in the 
color wheel, and enough hot water is added to wet them 
thoroughly and uniformly. The dry pigment may be thrown 
into the drum and sufficient water to float the stock added, 
or the pigment may be mixed with water and added through 
the trunnion ; but in either case the mill is run until all of the 
pigment has been absorbed. When this has taken place, the 
splits are removed from the drum and again dried in the 
drying wheel. After drying they are staked, trimmed, and 
sorted. The stock may be colored and fat-liquored at the 
same time without the intermediate drying, but better results 
are obtained by the method given. This method also permits 
a better selection for colors. 

Any of the mineral pigments may be employed in the above 

* This description was largely supplied by C. B. Kinney, a former student of the 
author, to whom he desires to give full credit. 



DYEING LEATHER 415 

process provided they are properly ground. Such colors as 
yellow ocher, chrome-yellow, chrome-green, iron oxides, zinc 
oxide, lithopone, burnt umber, and the like. 

The finish. — Pigment finish has to meet a number of re- 
quirements — it must go on evenly without giving a painted ap- 
pearance; it must withstand rubbing, boarding, and wetting; 
it must penetrate and have a fine appearance as regards bright- 
ness, luster, and evenness ; and it must not injure the leather 
or natural break. 

The first problem in making a finish is to get the pigment 
into suspension. There are a number of mediums in which the 
pigment may be ground, but the most commonly used is some 
form of soluble oil. The pigment is mixed to a thick paste 
with the oil and then ground in an iron or burrstone mill. 
Under ordinary circumstances 24 fluid ounces of oil will carry 
15 ounces of pigment to form a satisfactory paste. After 
the pigment has been ground it must then be added to the fin- 
ish. The nature of the finish varies with the results to be 
secured, and finishes are as numerous as the varieties of 
leather. They are made in the same manner as ordinary fin- 
ishes, and consist of solutions containing one or more of the 
following: shellac, casein, glue, blood albumen, egg albumen, 
gum, beeswax, Japan wax, soap, Irish moss, flaxseed, and all 
of the other finishing materials. 

When the finish is ready, the pigment is stirred in slowly. 
A solution of some coal-tar color is next introduced, either 
to shade or give fullness and brilliancy. A clear, brilliant 
and full color with pigment alone is impossible, as straight 
pigment shades are flat and dead. It is best not to use too 
much water, but use solutions of dye and then season the 
body by adding the pigment. When incorporating the pigment 
it is best to add a little of the finish to the pigment paste. 
This throws the pigment into a fine emulsion, which mixes 
readily with the main body of the finish. After mixing thor- 
oughly and diluting to the proper consistence, the whole solu- 
tion should be strained through a fine cheese-cloth, and it is 
then ready for application. A stirring machine should be used 



416 PRACTICAL TANNING 

at the table, so that the solution may be constantly agitated 
and thus prevent deposition of pigment. 

Hand seasoning. — The stock is passed through a seasoning 
machine, dried out, and again run through the machine. For 
these two coats a solution of coal-tar color, as near as possi- 
ble to the shade desired should be used. The leather is then 
thoroughly dried and glazed. It is then given two coats of the 
pigment finish, using a flat swab covered with fine plush. 
After each coat the leather is dried, and glazed after the second 
coat. In these two bottom coats the amount of pigment should 
be greater than in the subsequent coats. After glazing, the 
leather is smooth-plated and given three top coats, each top 
coat containing less pigment than the preceding one until the 
last coat, which should contain no pigment. The top coat 
should contain some albumen to give the required brilliancy. 
After the last top coat the leather is thoroughly dried, lightly 
staked, and smooth-plated. 

Machine seasoning. — The leather is dyed on the machine, 
as given under hand-seasoning, but the stock is not glazed. 
Three coats of pigment finish are now applied on the machine 
and when the last coat is dry the sides are glazed. Three more 
coats are then applied, and when dry, the leather is again 
glazed. The same procedure as given under hand seasoning 
should be carried out in machine-seasoning. 

Full grain finish. — If the finish is to be applied to full grain 
leather it must be of such consistence that it will be easily 
taken up by the stock and will not crack. The application is 
much simpler in this case than in the preceding ones, in that 
the dye coats are unnecessary. The only results required are 
an evenness of finish and a clear color. From 2 to 4 coats 
only are required, the leather being glazed after each applica- 
tion. For full grain leather hand seasoning is the most 
satisfactory. 

Blacking and stuffing chrome harness leather. — The 
leather, re-tanned, and shaved, is in condition to be blacked 
and stuffed. There are two methods : either the leather may 



DYEING LEATHER 417 

be blacked and then stuffed, or it may be first stuffed, then 
dried, buffed, and bleached. 

When the leather is blacked first and then stuffed, it is 
taken, a side at a time, set-out smooth on a table and blacked 
with logwood liquor and striker ; then it is washed, run through 
a wringer, and put into condition for stuffing. 

The logwood liquor is made of 6 lb. of logwood crystals 
and 2 lb. of borax in 50 gallons of water. The striker is 
made of 7 lb. of iron sulphate and 5 lb. of copper sulphate in 
50 gallons of water, although any good striker may be 
used. The leather, after it has been wrung, is ready to be 
stuffed, 100 lb. of it requiring 10 lb. of mineral wax, 10 lb. 
of best stearine and 5 lb. of good hard grease. These mate- 
rials should be boiled and thoroughly mixed, and applied 
hot to the leather in a warm drum. The leather is drummed 
40 minutes, then placed in piles, covered up and left until 
the next day. It is then struck out on the flesh side, hung up 
until partly dry, and next stoned out on the grain. The grain 
then gets a light coat of cod-liver oil, and is again gone over 
with the stone and slicker. The leather is then hung up to 
dry. 

The stuffing described above may be used, or a mixture of 
60 per cent stearine, 20 per cent tallow, and 20 per cent min- 
eral wax, heated to 190° F., 24 lb. being used for 100 lb. 
of leather. The leather is weighed and run a few minutes 
in the hot drum. The stuffing is then thrown in and the drum 
run 45 minutes. After lying in a covered pile over night, 
the leather is struck out on flesh and grain and hung up to 
dry. When it is partly dry, the grain is re-set, and the leather 
is then thoroughly dried. When dry, the scratches and im- 
perfections can be buffed from the grain, and it is then ready 
to be blacked with logwood and striker. A sig (a seasoning 
of adhesive compounds) is necessary to prepare the leather 
for the logwood. When blacked, the leather is washed off, 
set-out, and hung up to dry. 

Finishing. — This is done with mutton tallow and cod oil, 
3 lb. of the former and 2 lb. of the latter being melted 



418 PRACTICAL TANNING 

together, and the grain given a good coat with it, which is 
thoroughly glassed in. The leather is then left in a pile for 
24 hours, when it is re-glassed, this being the finishing touch. 

In case a dry feel is desired, the sides are seasoned with a 
solution of blood albumen, isinglass, and nigrosine in log- 
wood liquor, then dried and oiled off with hot paraffin oil, or 
with a mixture of paraffin and neat's foot oils. Sometimes 
a coat of starch decoction is applied to the flesh side. 

By using 7 lb. of quebracho liquor, 70° bk., for each side, 
weight and solidarity are given the leather. Chrome-tanned 
harness leather made by the methods that have been described 
has greater tensile strength and is more waterproof than 
ordinary bark-tanned leather. 



CHAPTER XIV 
FAT-LIQUORING 

In the production of leather of any kind, the use of oils, 
fats, waxes, or soaps, or a combination of these is absolutely 
necessary during some part of the manufacturing process. 
These materials are used either as part of the tanning process 
or are introduced to give strength and pliability to the product. 
The oils selected are chosen with a view of producing special 
results or of imparting certain characteristics to the leather. 

A discussion of oils is not within the scope of this book, 
but for those who desire more information on the general 
topic, reference may be made to the "Manual of Industrial 
Chemistry," written by the author of this treatise on tanning. 
It may not be out of place, however, to mention a few of the 
salient points which may be of value to the reader. 

Oils, fats, and waxes constitute a large class of substances 
which are of animal, vegetable, or mineral origin. True oils 
and fats are derived from animals, both terrestrial and ma- 
rine, and from vegetable sources, and consist chemically of 
a combination of fatty acids with glycerine. The nature and 
proportions of the fatty acids present determine whether a 
substance is an oil or a fat, but there is no distinct line of 
demarcation. What is a solid fat in cool climates may be 
liquid oil in a warm climate, so that some authorities prefer 
to make no distinction between fats and oils, simply calling 
one class liquid and the other solid. Solid fats usually con- 
tain a larger proportion of stearine. Most natural oils, how- 
ever, are mixtures of several fatty acids with glycerine. The 
chemical constituents of a fat may perhaps be better under- 
stood from the following formula: 

(CnH^COCOsCsHs (stearine) 

(C 17 H 33 COO) 3 C3H5 (olein) 

(C 16 H3iCOO)3C 3 H5 (palmitin) 

In other words, the above combinations constitute the prin- 

419 



420 PRACTICAL TANNING 

cipal ingredients of most oils, and the proportions of each 
determine whether it is liquid, pasty, or solid. In addition 
to these typical compounds, most fats or oils carry some other 
bodies which give them special characteristics. Depending 
upon whether the oils contain larger or smaller quantities of 
unsaturated fatty acids we have drying, semi-drying, and non- 
drying oils. 

Any oil, when treated with caustic alkali, undergoes a 
change which is called saponification, meaning the formation 
of soap. For example, if we treat tallow, which contains a 
large amount of stearine, with caustic soda, we have the fol- 
lowing reaction: 

(Ci 7 H 35 COO) 3 C 3 H 5 + 3NaOH = 3Ci 7 H 3B COONa + C 3 H 5 (OH) 3 
stearine caustic soda sodium stearate glycerine 

or soap 

This sodium stearate is what we are familiar with as soap. 
The character of the soap is influenced by the quantity of 
sodium stearate which it contains; the more stearate present 
the harder the soap. 

Waxes differ from oils and fats in that they are a combina- 
tion of fatty acids with higher alcohols. They do not lend 
themselves so readily to saponification as oils, but when they 
do so saponify the resulting product is a soap and a higher 
alcohol. Certain oils have the property of combining with 
sulphuric acid, forming what is known as sulphonated oils, or 
soluble oils, a more complete description of which will be 
given later in the text. 

Mineral oils are entirely distinct from true oils in their 
chemical composition, being a mixture of hydro-carbons which 
are incapable of saponification. These oils are derived mostly 
from petroleum, and are usually spoken of as petroleum or 
paraffin oils. These mineral oils range in fluidity from light 
mobile liquids to heavy wax-like substances. 

Oils of the above-mentioned classes are used in the produc- 
tion of leathers either for fat-liquoring, oiling, or stuffing. 



FAT-LIQUORING 421 

Their uses for various purposes will be seen in the following 

pages. 

Fat-liquoring process. — This is a process of much impor- 
tance in the finishing of leather. No matter how well tanned 
the hides or skins may be, if they are not properly fat- 
liquored they dry out stiff and lack that full, well-nourished 
feel that is so essential; the fat-liquor imparts to the leather 
the necessary fullness and softness. The process consists in 
treating the leather in a drum with a hot emulsion of soap, 
oil, and other ingredients, which is entirely absorbed by the 
leather. If given too much grease they work out too soft 
and cannot be finished satisfactorily. The fat-liquor should 
be a perfect emulsion; if it is not, the grain is likely to have 
a greasy feel and the colors a patchy appearance. Neat's foot, 
olive, castor, and sulphonated oils are generally considered the 
most suitable oils for fat-liquoring light leather ; egg-yolk and 
soap being sometimes combined with them. There are also 
several prepared fat-liquors and oils obtainable which are of 
much value. Commercial fat-liquors are carefully prepared, 
blended and aged, and containing no excess of alkali they pro- 
duce excellent results on both chrome and vegetable-tanned 
leather. Sulphonated oils require merely to be dissolved in 
hot water to be ready for use. The best way to use such 
oils, however, is to combine them with oil or grease, such as 
neat's foot or moellon degras. The sulphonated oil so used 
acts as the carrier and emulsifier of the other oils and greases. 

Before being fat-liquored, the leather is sometimes pressed 
or struck out to rid it of the surplus water, which would re- 
tard the penetration of the fat-liquor; but as a rule the fat- 
liquor is applied to the wet stock immediately after coloring. 
A suitable drum is heated with live steam to a temperature 
of about 140° F. for chrome-tanned leather and 120° F. for 
vegetable-tanned stock. Whatever water there may be in it 
is drained out, and the skins are thrown in and drummed for 
5 minutes to warm them. The hot fat-liquor is then poured 
into the drum through the hollow axle and the skins are 
drummed in it for 30 minutes, being then dipped into hot 



422 PRACTICAL TANNING 

water, placed smoothly over horses and covered up for several 
hours so that the grease may combine with the fibers. ' 

Fat-liquors for chrome-tanned sheepskins. — After these 
skins have been neutralized, washed, and shaved, they are either 
dyed and then fat-liquored, or fat-liquored and dyed after- 
wards. Some tanners combine the two processes, first dye- 
ing the leather in a drum and then running the spent dye liquor 
out and applying the fat-liquor. It is also practicable to add 
the fat-liquor to the dye liquor in the drum after the skins 
have assumed the desired color. The fat-liquor feeds and 
nourishes the leather. Sheepskins are naturally soft and do 
not require much fat-liquor; nevertheless, some grease and 
oil are required to impart to the leather the desired fullness 
and soft feel. When the fat-liquoring is a separate process, a 
suitable drum is heated with live steam, the leather is thrown 
in and drummed 10 minutes to warm it and make it more 
receptive to the fat-liquor. The fat-liquor is now poured into 
the drum through the funnel attached to the hollow axle and 
the leather is drummed with it for 30 minutes or longer, or 
until it has absorbed the oil and grease and left the water 
behind. After the process is finished, the leather is taken out 
of the drum, and if it was not previously colored, it should be 
rinsed in hot water, drained, and dyed; if it was colored be- 
fore it was fat-liquored, the custom is to strike it out, oil 
the grain, and hang it up to dry. Any one of the following 
formulas may be used with the assurance that the leather will 
be fat-liquored in a satisfactory manner: 

1. For 100 lb. of leather: 1 lb. of castile soap, 1 pint of 
neat's foot oil, and ^ lb. of egg-yolk. Boil the soap in 2 gal- 
lons of hot water; add the oil, and mix thoroughly. Then 
add cold water to make 12 gallons of liquor. When the tem- 
perature has been reduced to 120° F. by the cold water, add 
the egg-yolk and mix thoroughly. 

2. For each dozen skins to be fat-liquored, use 1 pint of 
egg-yolk, -| pint of olive oil, 4 oz. of castile soap, and 6 gal- 
lons of water. Chip the soap into the water and boil until it 
is dissolved ; then stir in the oil. Boil the mixture of soap and 



FAT-LIQUORING 423 

oil; cool down to 100° F., and add the egg-yolk. For glove 
leather, make a paste of 1 pint of flour and cold water and 
stir it into the soap, oil, and egg solution. Mix thoroughly, 
run it into the drum at 110° F., and mill the skins with it 
for 30 minutes. 

3. A fat-liquor considerably richer than the foregoing is 
made of 2\ lb. of neat's foot oil, | oz. of potassium carbonate, 
| lb. of potash soap, and f lb. of sulphonated oil. Mix and 
use the same as No. 2. This fat-liquor gives a well-nourished, 
springy feel to the leather, and there is no danger of spew. 

4. Chrome-tanned skins can be fat-liquored with egg-yolk 
and neat's foot oil. Such a fat-liquor is especially suitable for 
colored leather. For each dozen skins use 1 pint of egg- 
yolk and \ pint of neat's foot or olive oil. Beat the two 
thoroughly together and add warm water. Use at a tempera- 
ture of 125° F., and drum the skins with it for 30 minutes. 

5. For chrome-tanned glove leather: 1 lb. of olive oil soap, 
2 oz. of borax, \ lb. of neat's foot oil, and 2 lb. of egg-yolk 
for 100 lb. of leather. Apply before dyeing at a temperature 
of 125° F. 

6. For 200 lb. of skins, use soap, 8 oz. ; olive oil, 2 lb.; 
treated cod-liver oil, 2 lb. ; birch oil, 2 oz. ; and potassium car- 
bonate, 3 oz. Boil the soap, olive and cod oil in a few gallons 
of water, then add the birch oil. Stir the emulsion thor- 
oughly, then add the potassium carbonate dissolved in a little 
hot water. Add enough water to make 15 gallons of liquor, 
and use at a temperature of 160° F. 

7. A good fat-liquor for 200 lb. of heavy dull-finished 
leather is made of soap, 1 lb. ; neat's foot oil, 3 lb. ; moellon 
degras, 3 lb. ; and salts of tartar, 4 oz. Boil the soap and 
oil in a few gallons of water, then put in the moellon degras 
and stir thoroughly. Dissolve the salts of tartar in a little 
water; add the mixture and stir again. Run in enough water 
to make 24 gallons of liquor and apply to the skins at 150° F. 

8. The sulphonated oils now on the market are of value 
in fat-liquoring. The oil is dissolved in hot water and the 
leather is drummed with the solution either before or after 



424 PRACTICAL TANNING 

it has been colored. The oil can also be added to the dye 
liquor and applied to the leather in that form. It is generally 
best to pour it into the drum after the color has been taken 
up by the skins. • 

Neat's foot oil should not contain any solid fatty substance 
which is likely to separate at a low temperature and thus 
cause exudation, nor should there be any solid fatty acids in 
the soap. A small quantity of borax or sal-soda is often 
added to obtain a finer emulsion ; and the use of castor oil, 
Turkey red oil, or castor-oil soap is advisable when very pli- 
able leather is required. Fat-liquor should penetrate the 
leather easily and should not contain any ingredient likely to 
cause exudation or spewing. A greasy or sticky feel of the 
leather after fat-liquoring indicates insufficient neutralization 
or the presence of lime. Where leather is to be colored after 
it is fat-liquored it should, immediately after completion of 
that process, be dipped in clean, hot water, to remove surface 
oil. This rinsing in hot water clears the grain, so that the 
mordant and dye "take hold" more readily. 

Fat-liquoring chrome-tanned calfskins. — After calfskins 
have been tanned into leather by a process of chrome tan- 
ning it is necessary to treat them with oil or grease in some 
form so that they may be finished into soft, well-nourished 
leather. The quality of the finished product depends largely 
upon how this process is applied, and what materials are used. 
Nothing that seriously affects the color or makes the leather 
greasy or spotted can be used. The skins can be fat-liquored 
either before they are colored or afterwards, the usual cus- 
tom being to do the work before coloring in order that the 
fat-liquor shall not injure the color. Black leather, however, 
is usually fat-liquored after it has been blacked. Some tanners, 
in order to save labor, do not wash their leather after dyeing 
it; they simply drain off the spent dye liquor and run in the 
fat-liquor, and in some cases the dye liquor is not even 
drained off, the fat-liquor being added after the leather is 
colored. The oil and grease are employed in the form of an 
emulsion, which is readily taken up by the leather. 



FAT-LIQUORING 425 

The skins are generally shaved before being fat-liquored; 
but some prefer to shave after blacking. When this is done, 
only half of the dye required for shaved leather is used, nigro- 
sine or other color must be added to the fat-liquor to cover up 
the unevenness produced by shaving. 

Sulphonated oils are of great value to the tanner of chrome 
calfskins. Combined with neat's foot oil and moellon degras, 
the sulphonated oil acts as an emulsifier and carrier of the 
others. The following fat-liquors can be used on black or 
colored leather with perfect safety: 

1. Take 6| lb. of neat's foot oil and heat to about 160° 
F. Dissolve 2\ lb. of potash soap in hot water, stir it into 
the oil, and mix thoroughly. When the mixture has cooled 
slightly, add d\ lb. of sulphonated oil and mix well. Three 
pounds of this mixture dissolved in 12 gallons of hot or boil- 
ing water will fat-liquor 100 lb. of leather. 

2. A richer fat-liquor, which gives a better-nourished feel 
to the leather, is made of 12| lb. of neat's foot oil, 2\ oz. of 
potassium carbonate, 3f lb. of potash soap, and 4 lb. of sul- 
phonated oil. Heat the neat's foot and the potash to 160° 
F. ; add the dissolved soap, and stir well; cool slightly and 
add the sulphonated oil, stirring the mixture thoroughly. Use 
3 lb. of this mixture dissolved in 12 gallons of hot water for 
each 100 lb. of leather. 

3. An excellent fat-liquor is made of soap, oil, and degras. 
For 100 lb. of leather use, fig or olive oil soap, 1 lb.; neat's 
foot oil, 2 lb. ; moellon degras, 2 lb. ; and caustic soda, 1 oz. 
Boil the soap in a few gallons of water until it is d' solved ; 
then add the oil and boil the mixture for 15 minutes. Then 
stir in the moellon degras, adding the caustic soda dissolved 
in water. Add water to make 12 gallons of fat-liquor; use 
at 125° F., and run the leather in it for a half-hour 

4. The following is a good fat-liquor for colored leather : 
Soap, 1 lb. ; olive oil, 2 lb. ; treated cod oil, 2 lb. ; birch oil, 
2 oz. ; and salts of tartar, 3 oz. Boil the soap until it is dis- 
solved; add the olive and cod oils, and boil several minutes; 
then stir in the birch oil and the salts of tartar dissolved in a 



426 PRACTICAL TANNING 

little water. Add enough water to make 12 gallons of liquor, 
and use it at 125° F. 

5. Castor-oil soap and castor oil make an excellent fat- 
liquor for colored skins. A half pound of the soap and f 
lb. of the oil may be used in 10 to 12 gallons of water for 
each 100 lb. of leather. 

6. Neat's foot oil and cod oil are used in another liquor, 
1 pint of each being stirred together with 1 pint of a 10 per 
cent solution of soda, and the mixture added to a hot solu- 
tion of 3 lb. of soap chips in 6 pints of boiling water; 5 or 
6 lb. of the mixture is used for 100 lb. of the shaved skins. 

7. For light-weight colored skins, a satisfactory fat-liquor 
is made of Castile soap, 1^ lb.; neat's foot oil, 1| pint; egg- 
yolk, |- lb., for 100 lb. of leather. Dissolve the soap in a 
pail of hot water, then add the oil, and when cool the egg- 
yolk, and mix well. Make up to 12 gallons and use at 125° F. 

8. One pound of fig or other good soap, 4 lb. of treated cod 
oil, 2 lb. of moellon degras, and 1 oz. of caustic soda is par- 
ticularly suitable for dull-finished leather. Boil the soap; add 
the oil and boil again ; then add the degras and soda and stir 
for 5 minutes. There should be 12 gallons of the liquor, used 
at 125° F., and the leather drummed with it for a half-hour. 

9. A fat-liquor made according to the following formula 
is suitable for either black or colored leather, and is quite 
satisfactory : Olive-oil soap, 1 lb. ; borax, 1| oz. ; neat's foot 
oil, ^ lb. ; egg-yolk, 1^ lb., for 100 lb. of leather. Boil the soap 
in 2 gallons of water; dissolve the borax in a little hot water, 
and stir it into the neat's foot oil; add water to reduce the 
temperature to 90° F., and stir in the egg-yolk. Make up to 
12 gallons, and apply at a temperature of 125° F. The fat- 
liquor is usually absorbed by the leather in 30 minutes. 

10. Sulphonated oil alone, or mixed with neat's foot, cod, 
or moellon, gives satisfactory results on chrome-tanned calf. 

Oiling the leather. — When the fat-liquoring is finished, the 
skins should be placed smoothly over horses to drain several 
hours. They are next struck out on the grain side and oiled. 
The water should be pressed out of the leather before the 



FAT-LIQUORING 427 

oil is put on so that the latter can quickly penetrate into the 
body of the skins where it will add strength to the fibers. For 
the oiling there is none better than neat's foot, which is used 
alone and also in combination with paraffin oil. For a bright 
finish, a mixture of 1 part neat's foot and 3 parts paraffin oil 
is sometimes used; for dull leather, equal parts of the two 
oils. 

It is advisable to apply the oil hot to the leather, and avoid 
oiling the flanks, after which they are hung up to dry. It 
is best to dry them rather slowly in a moderately warm room 
with a good circulation of air. 

Fat-liquoring chrome-tanned kangaroo. — 1. An acid 
fat-liquor recommended for kangaroo leather is made of sul- 
phonated oil and neat's foot oil. Mix 6| lb. of the latter oil 
with 6| lb. of sulphonated castor oil, and make a rich emulsion 
with water. Three pounds or less of this fat-liquor, diluted 
with 10 gallons of water at 140° F., is enough for 100 lb. 
of leather. The addition of | lb. of ammonia is recommended 
where there is a slight trace of acid in the stock. 

2. A fat-liquor somewhat richer than the foregoing, which 
gives a well-nourished leather, is made of 12| lb. of neat's 
foot oil, 2\ oz. of potassium carbonate, 3f lb. of potash 
soap, and 4 lb. of sulphonated oil. Dissolve the carbonate in 
a little hot water, and stir it into the neat's foot, and heat 
the oils to 160° F. Then add the potash soap and stir it 
thoroughly. Shut off the steam and add the sulphonated oil, 
stirring thoroughly until a perfect emulsion results. This 
fat-liquor gives a good feel, and the leather can later on be 
finished in dull or glazed. 

3. This is also recommended: fig or olive oil soap, 1 lb.; 
neat's foot or cod oil, 2 lb. ; moellon degras, 2 lb. ; and caustic 
soda, 1 oz. Boil the soap in 6 gallons of water until it is 
dissolved; add the oil and boil 15 minutes; then add the moel- 
lon degras, and stir 5 minutes. The caustic soda, dissolved 
in 2 quarts of water, is added last. Enough cold water should 
then be introduced to make 12 gallons of fat-liquor for 125 
lb. of leather. 



428 PRACTICAL TANNING 

4. The following fat-liquor and No. 3 are recommended for 
dull-finished leather: moellon degras, 3 lb.; and salts of tar- 
tar, 4 oz. Dissolve the latter in 3 gallons of hot water; then 
stir in the degras, and stir thoroughly for several minutes ; 
finally adding enough water to make 12 gallons of liquor. 
Use at 140° F. 

Applying the fat-liquor. — An approved method of fat- 
liquoring chrome-tanned kangaroo leather is first to dye the 
skins black and then wash them, pressing or striking out the 
surplus water. The clean drum is heated with live steam ; 
the water is drained out, then the leather is thrown in and 
drummed a few minutes to warm it. The hot fat-liquor is 
finally poured in and the leather is drummed for 40 minutes. 

All of the grease should be taken up by the leather, leav- 
ing nothing but clear water behind. Some tanners use the 
following method : The leather and a quantity of hot water 
are put into the drum and run 10 minutes. The drum is 
then stopped and the fat-liquor in a slightly concentrated 
form is poured in, and, mixing with the hot water, accom- 
plishes its purpose. It is also customary to add the hot fat- 
liquor to the dye liquor after the color has been exhausted. 
Finally the leather is placed over horses to drain at least 12 
hours; it is then set out, oiled on the grain with neat's foot 
and glycerine, and hung up to dry. 

Fat-liquors for chrome side leather. — The fat-liquoring 
of chrome-tanned grain leather may be done before coloring 
or blacking, or immediately afterwards. The preferred method 
is to fat-liquor leather before it is colored, and black 
leather after it has been dyed. The methods given under 
chrome calf and kangaroo leather will work equally well on 
this class of stock. 

Fat-liquoring vegetable-tanned side leathers. — In the 
finishing of sides into dull and glazed boarded grain leather, 
imitation kangaroo as well as black and colored Russia leather, 
a not uncommon practice is to give the goods two applica- 
tions of fat-liquor, one before and one after coloring. Both 
fat-liquors may be sulphonated oil, or the first may be a solu- 



FAT-LIQUORING 429 

tion of the sulphonated oil, and the second an emulsion of 
oil, soap, and degras. The procedure is as follows: After 
the leather has been split, re-tanned, pressed, and shaved, it is 
sammied and then weighed for the first application of fat- 
liquor. The drum is heated with live steam to 125° F., and 
the leather put in with a small quantity of hot water, and 
drummed until it is filled and the moisture evenly distributed, 
the fat-liquor being thus rapidly absorbed. Another way to 
moisten the leather is to dip it into warm water and place it 
in piles until it is softened throughout, this being less likely 
to "pipe" the grain than dampening in the drum. An excess 
of water in the drum or in the leather must be guarded against, 
as it prevents absorption of the fat-liquor. After having re- 
ceived the first application of fat-liquor, the leather is rinsed 
off in clean water to free it from particles of leather fiber and 
fleshings, which, containing oil, are liable to spot the leather 
while it is drying. Previous to being hung up to dry, the 
leather should be placed on a horse for a few hours to allow 
the fatty matter to penetrate. 

When leather is given two applications of fat-liquor, the 
first treatment should be at least half of the whole quantity 
used. Colored leather can be given no better fat-liquor than 
sulphonated oil, used alone or combined with neat's foot or 
degras, such fat-liquor being also good for black leather. A 
thoroughly emulsified fat-liquor of soap, oil, and degras is 
also suitable, while some tanners prefer to buy a commercial 
^at-liquor rather than make it themselves. 

Glazed and boarded grain leather is colored blue on the 
flesh side before the second application of fat-liquor, and 
blacked upon the grain afterwards ; flesh and grain may also 
be dyed at one operation if desired. 

Colored Russia leather is usually bleached, mordanted, and 
colored previous to the second application of fat-liquor. 

When dry from the first application of fat-liquor, the 
leather is dampened and colored, then dried and dampened 
again for the second fat-liquoring. Imitation kangaroo and 
dull grains are usually yellow-backed before the second ap- 



430 PRACTICAL TANNING 

plication of fat-liquor. After it is fat-liquored, the leather 
is again dried for finishing. Kangaroo calf and sides are 
sometimes fat-liquored and dried, then yellow-backed, grain- 
blacked, dried, and finished. The leather may be washed after 
re-tanning; pressed and fat-liquored; dried, and then colored 
and finished. 

Quebracho, gambier, and combination-tanned leather can 
be handled satisfactorily in the following manner : When the 
re-tanning is completed, the sides are washed and pressed to 
remove surplus liquor. After pressing, the leather is shaved 
and fat-liquored. In some cases it is drummed with sulphon- 
ated oil and dried before it is fat-liquored, this being a good 
method to follow in finishing colored leather. A drum is 
heated with steam to 100° F., and 1 gallon of sulphonated 
oil is used for 150 lb. of leather, weighed after pressing and 
shaving. The leather is drummed with the oil for a half-hour, 
then hung up and dried. After drying, the leather is weighed, 
dampened with warm water, and placed in piles to soften. 
It is then put into the drum and run with just enough water 
to soften it uniformly, when it is in condition to receive the 
fat-liquor. This method is entirely practicable and satisfac- 
tory, but some tanners omit the oil and fat-liquor the leather 
after it has been drained and pressed. 

To fat-liquor the leather, the drum should be heated to 125° 
F. with live steam, and the leather drummed in warm water 
until it is soft and full. The fat-liquor should be given to 
the leather in portions of. 1 to 2 gallons at a time through the 
hollow gudgeon, and after all of it is in the mill, the leather 
should be drummed 40 minutes. After being taken out of the 
mill, the leather should be rinsed in clean Warm water, drained, 
and dried. When dry, it may be colored blue on the flesh and 
black on the grain, or yellow upon the flesh and black on the 
grain ; or it may be colored any shade desired, dried, and fin- 
ished with smooth, boarded or printed grain, or into imita- 
tion kangaroo leather. 

The following fat-liquors have been used in tannery prac- 
tice, with good results : 



FAT-LIQUORING 431 

Fat-liquor formulas. — 1. Boil 25 lb. of potash soap in 25 
gallons of water until it is dissolved. Add 50 lb. of English 
sod oil and 6 quarts of neat's foot oil to the solution, and stir 
for several minutes. A few pounds of moellon degras may 
also be added. Enough cold water is next introduced to make 
50 gallons of liquor, and 20 gallons of this liquor suffices for 
100 lb. of dry leather which has been run in sulphonated oil 
previous to being dried. The exact quantity to use, how- 
ever, varies with the tannages, the quantity stated being the 
maximum ; but a smaller quantity will in most cases produce 
the desired result. 

2. Five pounds of soap and one gallon of moellon degras 
boiled and made into a fat-liquor with a half barrel of water 
is sufficient for 400 lb. of leather. It may be applied to the 
leather immediately after tanning, or the leather may be 
drummed with a little sulphonated oil and dried before it 
is fat-liquored. 

3. A good stuffing for imitation kangaroo and dull-printed 
sides is made of 12 lb. of cod oil to each 100 lb. of leather, 
dried after re-tanning, and weighed after it is dampened. 
Use at 130° F. Pack the leather down over night to harden; 
then set it out by hand and hang it up to dry. When dry, 
buff off the grain, trim, and stake the leather; then color the 
flesh yellow, and black the grain and finish the leather. 

4. For hemlock, quebracho, gambier, and combination- 
tanned leather, the following fat-liquor is recommended: 10 
lb. of soap, 4 gallons of neat's foot oil, and 10 lb. of degras 
to a barrel of liquor. Use at 125° F., preferably after color- 
ing; then set the leather out, oil the grain, and hang up to 
dry. The leather, dried after re-tanning, is dampened, col- 
ored, and then fat-liquored, when the grain is struck out and 
oiled with neat's foot, and the sides are then tacked on frames 
to dry. Ten gallons of this fat-liquor is sufficient for 25 
sides of 20-foot 4-ounce leather. It is best to use the liquor 
after the leather has been dyed black, or colored. 

5. For bright printed or boarded grains, another suitable 
fat-liquor is 12 lb. of pure cod oil, 2 lb. of French degras, and 



432 PRACTICAL TANNING 

2 gallons of thin soft soap for 100 lb. of damp leather. 
Apply at 125° F. The leather, after being re-tanned, should 
be drummed for an hour in warm, strong sumac liquor; then 
rinsed, scoured on both sides, and hung up to dry. When 
dry, it is dampened and fat-liquored, set out, and a light coat 
of oil applied to the solid parts of the flesh side. The leather 
should be set out very hard on both sides, since the tighter 
it is set the finer and more even the grain will be when the 
leather is finished. When dry, the leather is dyed black, 
dried, staked, and finished. 

Fat-liquoring vegetable-tanned calfskins. — The fat-liq- 
uors described under side leather are suitable for quebracho, 
gambier, hemlock, and combination-tanned calfskins; and can 
be applied to the leather immediately after it is tanned, or 
later, after it has been dried and colored. 

Fat-liquoring is one of the most important processes in the 
manufacture of calf leather. Only the best grades of ma- 
terials should be used, so that the leather will not be greasy, 
gummy, or liable to spew after it is finished. Sulphonated 
oil unites with the fibers of the leather and does not decom- 
pose in the leather; it also prevents greasiness and darkening 
of the grain. 

From the scientific point of view there is yet a great deal 
unknown regarding the action on leather of those emulsions 
of oil and soap which are technically termed fat-liquors. As 
now used on many varieties of bark and combination-tanned 
leathers, fat-liquor is a development of chrome leather manu- 
facture. Indeed, it is no exaggeration to say that the suc- 
cess of the chrome leather industry was dependent upon the 
discovery and application of fat-liquors; and even today the 
use of a proper fat-liquor is necessary for the production of 
a marketable product. 

To a considerable degree, the formulas for various fat- 
liquors are among the most carefully guarded secrets of a 
leather manufacturer; yet in the main the composition and 
method of preparation of a good quality of fat-liquor has 
become well known. Practically, a fat-liquor can be defined 



FAT-LIQUORING 433 

as an emulsion of oil and water, usually containing soap 
and frequently other emulsifying agents. Its purpose is to fill 
or nourish the leather and keep it from drying hard or brittle. 

Although the claim has never been put forward, Robert 
Foerderer, the inventor of "vici kid," the first merchantable 
chrome leather, is accredited as being the real inventor of the 
emulsified fat-liquor; yet according to all evidence, it was 
the use of the fat-liquor which made vici leather far superior 
to the products of other leather manufacturers. When the 
knowledge concerning the use of emulsion of oil began to leak 
out, other manufacturers then started to make good chrome 
leather. 

Having described the methods for producing fat-liquors, it 
will perhaps be well to consider their general constitution and 
the properties of their ingredients. An emulsion is a mixture 
of liquors that are mutually insoluble, but which are so mixed 
that fine particles of one are suspended in the other. The 
term is usually, although not necessarily, applied to mixtures 
of oil and water. Milk is often cited as the most perfect of 
emulsions. In order that an emulsion may be at all perma- 
nent, it is generally necessary that a third substance, called 
an emulsifying agent, be present. Such agents act by increas- 
ing the viscosity of the one liquid in which the fine particles 
of the other liquid are suspended to such a degree that the 
tendency to separate into different layers is largely overcome. 
In the case of milk, the casein, or milk albumen, acts as an 
emulsifier. In the familiar example of cod-liver oil emulsions 
of the pharmacy, the agent used is gum acacia or gum arabic. 
For leather manufacture it has been found that neither the 
casein of milk, nor gum arabic, nor indeed any other gum acts 
suitably as an emulsifying agent in fat-liquors. Primarily, 
they make trouble by perceptibly stiffening and harshening the 
leather, and then their power to increase viscosity diminishes 
rapidly with a slight increase in temperature. Soap has there- 
fore become largely used as the emulsifier in the preparation 
of fat-liquors. Regarded simply as such, soap is not es- 
pecially effective, but it has the extremely important advan- 



434 PRACTICAL TANNING 

tage, that is, provided the right kind of soap is used, that it is 
absorbed by the leather and does not injure it. To increase 
the efficiency of soap, or to replace it, two other emulsifying 
agents are used, namely, egg-yolk and sulphonated oils. The 
former is itself an emulsion, and the emulsifying agent in it 
is known as vitellin, an albumen considerably resembling 
casein. Presumably, because the proportion of oil and albu- 
men in the egg-yolk to the water contained in it is greater 
than in milk, it can be used in relatively greater proportion; 
egg-yolk is therefore much more efficient in a fat-liquor than 
milk. 

Sulphonated oils. — The subject of sulphonated oils is a 
large one and can be only briefly considered here. The best 
known of these is Turkey red oil which is largely used in the 
textile industry, especially in the dyeing of Turkey reds, hence 
the name. It is made by the action of sulphuric acid on cas- 
tor oil. Its manufacture requires considerable care, and it is 
best made on a large scale in factories specializing in its 
production. Inasmuch as leather manufacturers using it have 
generally desired to keep that fact secret, they have endeav- 
ored to manufacture it for their own use rather than purchase 
it from an experienced maker, but such manufacture is usu- 
ally attempted with imperfect apparatus, as well as inadequate 
knowledge. In the first place, castor oil is practically the only 
oil that can be sulphonated in the true sense, because the prin- 
cipal fatty acid in castor oil is ricinoleic acid, an unsaturated 
acid. This does not mean that other oils than castor cannot 
be treated with sulphuric acid, and some sort of a product 
obtained ; nor should it be understood that it is impossible to 
sulphonate fatty acids other than ricinoleic acid. For exam- 
ple, the fatty acids of linseed oil are largely unsaturated, but 
unless extraordinary precautions are taken to cool the mixture 
of acid and oil, the reaction is so violent that what is known 
as secondary reactions take place and the fatty acids are 
largely destroyed. 

The tendency of linseed oil to become resinous does not 
recommend it as a good leather lubricant. The more com- 



FAT-LIQUORING " 435 

mon practice is to treat oils, for example, neat's foot and 
tallow, whose fatty acids are principally acids of the oleic acid 
class. Oleic acid sulphonates only at a high temperature, and 
when an attempt is made to sulphonate one of the oils con- 
sisting largely of this substance, no sulphonation results; but 
the oil is simply broken up by hydrolysis and separates into its 
constituent parts, namely, fatty acid and glycerine. 

Casein. — This has been employed as an emulsifying agent, 
but the fact that it is soluble only in alkaline solutions, makes 
its use objectionable. Also the liability of casein solutions to pu- 
trefy is a disadvantage, especially as the usual antiseptics pre- 
cipitate it. Probably the most satisfactory preservative for 
casein solutions is white arsenic, only a very small quantity 
being needed, and so little arsenic remains in the leather that 
no objection can be raised to its use. One part of arsenic to 
two thousand parts of fat-liquor is a proportion that has 
been used with success. 

Egg-yolk. — This, as has been stated, is a valuable constit- 
uent of fat-liquors. It is itself an emulsion in which an al- 
bumen similar to casein is the emulsifying agent. Probably 
one reason for the superiority of egg-yolk to casein is that, 
in the case of the latter, the natural emulsion is broken up, 
while the former is used in an unchanged state. There is a 
sufficient excess of albumen in egg-yolk over that required to 
emulsify the natural oil it contains to make it suitable for 
holding large proportions of other oils in a state of emulsion. 
It is for this purpose that it is valuable in fat-liquors. Unfor- 
tunately, some dealers in the material add other oils to the 
egg-yolk, which while not necessarily deleterious to the fat- 
liquor, they reduce the emulsifying power of the egg-yolk, 
and so are rightly considered an adulteration. Still 
more reprehensible is the practice of adulterating egg-yolk 
with emulsions of oils and casein, which are colored by aniline 
dyes. An easy test is the addition of a small quantity of 
ammonia to one portion of a suspected sample, and a little 
acetic or muriatic acid to another. If either the ammonia 
or the acid produces a decided color-change in the egg-yolk, 



436 PRACTICAL TANNING 

it Indicates the presence of an aniline yellow, and is presum- 
ably an adulterated product. 

Potash soaps. — These are preferably used as the soap con- 
stituent of fat-liquors. The reason for this is that they are 
soft soaps, that is, have a lower melting point than the hard 
or soda soaps. The objection to the high melting point — or 
to express it another way, the low solidifying point — of the 
soda soaps is that it causes white specks or soap crystals to 
form in the leather, which is one variety of the familiar spew- 
ing, an especially annoying defect in finished leather. 

While all of the potash soaps are softer than the corre- 
sponding soda soaps, that is, those made from the same oils or 
fatty acids, one prepared from a hard, solid fatty acid will 
be nearly as hard as a soda soap made from a liquid fatty 
acid such as oleic acid. Also, if a soda soap is made from a 
liquid fatty acid, and a large percentage of water is allowed 
to remain in it, it will closely approximate the appearance of a 
potash or genuine soft soap. A simple drying test will, how- 
ever, serve to distinguish the true from the false. In order 
to appear soft, a soda-soap must contain a high percentage 
of water, which will evaporate and the soap remain behind 
hard and dry if a small sample is exposed a few hours to 
gentle heat in a shallow dish. Potash soaps, on the other 
hand, will not dry out hard unless made from hard fat. 

Fig soap. — A soap which has had much vogue for fat-liq- 
uor purposes is the so-called fig soap. It was originally a 
potash soap made from olive-oil foots. Much of the fig soap 
on the market is made from a mixture of olive-oil foots, 
cotton-seed oil, and tallow, and in appearance is much supe- 
rior \o that made exclusively from olive-oil foots. 

For practical use, a soap is probably better made in the old 
way, as the hard stearic acid soaps (from the tallow) will 
crystallize in the leather and cause spewing. 

The use of rosin oils must be especially avoided. These 
oils are obtained by the distillation of rosin, and while they 
are saponified, the products so formed have but few of the 
properties of ordinary soaps, and are unsuitable in fat-liquors. 



FAT-LIQUORING 437 

The free fatty acids of rosin oils are objectionable as they 
oxidize and become resinous or gummy. Some sulphonated 
rosin oils have been offered for fat-liquoring purposes, but 
from theoretical considerations there is no reason to suppose 
that they will have sufficient efficiency to replace castor-oil 
compounds. A final word in regard to fat-liquors is the ques- 
tion of alkalinity or acidity. The first fat-liquors were essen- 
tially alkaline, on account of their large soap content; while 
the sulphonated oil compounds have an acid nature. If alka- 
line and acid fat-liquors are mixed, as frequently has been the 
case, the possible good effects of either when used separately 
are nullified. 

The effects on colors should also be considered, and it 
should be especially remembered that an acid fat-liquor has 
much less effect on colors than one which is alkaline or con- 
tains a considerable quantity of soap. 

How to make and use sulphonated oils. — A sulphonated 
oil is one that has been subjected to the action of sulphuric 
acid. The oils that can be sulphonated are castor, neat's 
foot, olive, cod, corn, and a few other saponifiable oils. Those 
that have been treated by the process of sulphonation have 
come more and more into use in the manufacture of heavy 
and light leathers. They are especially useful in fat-liquoring 
vegetable and chrome-tanned leather. 

During the process of manufacturing sulphonated oil, the 
acid must be added to the oil very slowly; the oil should be 
thoroughly stirred while the acid is being added to it and also 
while it is being washed out. To obtain the best result, the 
oil must be chilled while it is being acidified. The following 
instructions will enable anyone to prepare a usable sulphon- 
ated oil : Take a barrel and saw it in two parts just below 
the two hoops near the top. This makes a tub of convenient 
size. Then put a 15-gallon crock into the tub and surround 
it with cold water. If the water is not below 60° F., add 
ice to lower its temperature, as it must be cold enough to chill 
the oil. Put 6 gallons of castor oil into the crock and stand 
over night to become thoroughly cool. 



438 PRACTICAL TANNING 

The next morning carefully pour 6 oz. of 66° Be. sulphuric 
acid into the oil, and stir for at least 5 minutes after the 
acid has been added. Three hours later introduce 6 oz. more 
of acid, taking care to add it slowly and to stir thoroughly. 
Four hours later stir in another 6 oz., and two hours later 
6 oz. more should be added with careful and thorough stirring. 
The next morning add 6 oz. of acid to the oil, and every 
3 hours thereafter add 6 oz. until 24 oz. have been added on 
the second day. 

On the morning of the third day take a clean barrel, and 
put a wooden spigot into it as near the bottom as possible. 
Place the barrel on a box or a block so that it will be 6 or 8 
inches off the floor. Pour the acid-treated oil into the barrel 
and fill the latter two-thirds full of luke-warm water. Add 
30 lb. of salt to the water and oil, and stir for 15 minutes. 
Repeat the stirring every half-hour for 5 hours ; then allow the 
oil to rise to the top, open the spigot, and let the salt water 
run off until oil begins to show. Close the spigot and fill the 
barrel with warm water as before; then add 24 lb. of salt and 
stir for 15 minutes. Allow the oil and salt water to stand 
again over night, then draw off the water as before, and fill 
the barrel again with water, adding 18 lb. of salt, stirring as 
before. Draw the water off again and fill the barrel with 
warm water and put in 15 lb. of salt. Stir thoroughly for 10 
or 15 minutes, and allow the oil to stand over night. The next 
morning draw the water off, and the oil that remains in the 
barrel is ready for use. In order to get a satisfactory prod- 
uct, the oil must be well stirred when washing out the acid ; 
and the acid must never be put in fast enough to burn the oil. 

To keep the oil, add a little water to it — about twice its 
own weight. Before adding the water, stir in enough concen- 
trated ammonia to neutralize whatever acid there may be in 
the oil, also to carry it to the alkaline side. 

Neat's foot oil and cod-liver oil mav be combined and sul- 
phonated in the following manner : Mix 30 lb. of neat's foot 
and 20 lb. of cod in a 20-gallon crock standing in a tub con- 
taining: cold water. Add ice to the water to lower the tern- 



FAT-LIQUORING 439 

perature below 65° F. Put the oil in the crock before closing 
down for the night, and in the morning it will be chilled. 

For the 50.1b. of oil, use 88 oz. of sulphuric acid, dividing 
it into four equal portions. At about 8 a. m. pour one por- 
tion of 22 oz. of the acid very slowly into the oil, stirring 
while it is being added and continue for 5 minutes afterward. 
This should take about 15 minutes. Allow the oil to stand 
until 5 p. m. Then add another portion of the acid, stirring 
thoroughly as in the morning. Let the oil stand until the 
next morning; then add another portion of acid as before. 
At about 5 p. m. on the second day add the last portion of 
acid, stirring thoroughly as before, taking 15 minutes. On 
the morning of the third day, the acid-treated oil is in con- 
dition to be washed. Use a large barrel or tub holding 100 
gallons, provided with a spigot, as mentioned above. Put 
the oil into the tub or barrel, and add enough water at 100° 
F. to fill the tub nearly half full. To the water add a pail of 
Glauber's salt and stir thoroughly, then add more water until 
the tub is nearly full. Allow this to stand until towards eve- 
ning of the third day, then open the spigot and let the water 
run off. Close the spigot and fill the tub as before with warm 
water, and add a little less than a pail of Glauber's salt. Al- 
low the mixture to stand until the next day, and then draw 
off the water the same as before. Fill up the tub again with 
warm water and I5 pails of common salt. Stir the oil and 
the water thoroughly, and allow the mixture to stand 12 hours. 
Then draw off the water and fill the tub again nearly full 
with warm water, and add 1-J pails of salt. Stir the oil well, 
and let the mixture stand until the next day. The water 
should then be drawn off, when the oil is ready for use. 

A method which is used extensively and saves considerable 
time in washing consists in treating the sulphonated oil with 
a volume of water as indicated under washing, and to the 
water add sodium carbonate in place of the salt. The sodium 
carbonate at once combines with the sulphuric acid, forming 
sodium sulphate or Glauber's salt. The oil is thus neutralized, 
separated, and washed in one operation. Care, of course, 



440 PRACTICAL TANNING 

should be taken not to add too great a quantity of the alkali, 
otherwise there would be danger of saponification. 

Sulphonated oil on chrome leather. — When the oil has 
been properly treated with acid and washed, it dissolves read- 
ily in hot water. When using, it is dissolved in water and the 
leather is drummed with the solution ; 100 lb. of chrome leather 
may be fat-liquored with 4 to 6 lb. of the oil dissolved in 12 
gallons of water at 125° F. The drum used for the. purpose 
should be perfectly clean, and the leather warmed in a hot 
drum before it is given the fat-liquor. The exact quantity of 
oil to be used must be determined by the operator, and depends 
upon the degree of softness desired. Drum the leather in the 
fat-liquor for 30 minutes ; then take it out and rinse it off in 
hot water to remove the oil from the surface. This washing 
is necessary when the leather is colored after fat-liquoring. 
If colored before fat-liquoring, rinse the leather, let it drain 
a few hours, strike it out, and hang it up to dry. 

The best results, however, are secured when the sulpho- 
nated oil is combined with neat's foot oil or some other fat- 
liquoring material. Used in this way, it emulsifies the other 
oils and greases and carries them into the leather. When neat's 
foot or moellon degras is used with the sulphonated oil, the 
leather becomes lubricated internally, and has, when finished, 
a full, well-nourished feel. 

Sulphonated oil on vegetable-tanned leather. — Vegetable- 
tanned skins may be fat-liquored with a solution of the sul- 
phonated oil, with a mixture of such oil and mineral oil, with 
a mixture of sulphonated oil and neat's foot oil, or with a mix- 
ture of either sulphonated cod oil or sulphonated neat's foot 
oil and mineral oil. Of these combinations, the best is un- 
doubtedly the mixture of sulphonated castor oil and neat's 
foot oil. The emulsion can be given to the leather imme- 
diately after tanning and before the skins are dried ; it can 
also be brushed on or mixed with the tanning liquors toward 
the end of the drum tannage. Bark and extract-tanned leather, 
after it has been split and re-tanned, may be fat-liquored with 
a mixture of fish oil emulsified with sulphonated castor or 



FAT-LIQUORING 441 

neat's foot oil. The mixture of oils can also be added to the 
re-tanning liquor in the drum, thus giving fullness and a soft 
feel to the leather. 

Sulphonated oil on sole leather. — Another important use 
for sulphonated oils is in the extracting of sole leather. When 
sole leather is re-tanned in the drum it is of great advantage 
to add to the liquor mineral oil to which sulphonated oil has 
been previously added. This sulphonated oil is soluble in 
water, with which it forms a more or less thick paste, and 
mixes with mineral oil. The presence of the sulphonated oil 
enables the mineral oil to penetrate the leather in small quan- 
tities, and, without destroying its firmness allows it to retain 
a certain interior humidity. The presence of the mineral oil 
and of the sulphonated castor oil has also another object, 
namely it facilitates the penetration of the tannin into the 
leather, and by lubricating the inner portion, prevents 
damage by rubbing of the grain against the sides of the 
drum. 

Castor-oil soap. — This is an excellent material for fat- 
liquor. It can be made in the tannery in the following man- 
ner : Dissolve 2 lb. of caustic soda in 1 gallon of water. Heat 
2\ gallons of castor oil to 90° F., then pour the soda solution 
into the warm oil, and stir the mixture until it becomes thick. 
Cover the tub containing the soap, and let it stand over night 
in a warm place. The soap is ready for use the next day. 
It is advisable, but not absolutely necessary, to melt the soap 
again in a jacketed pan fitted with a stirring apparatus, by 
means of which a more thorough mixing of the soap is 
obtained. 

Potash soap. — For any purpose for which a potash soap is 
required it is essential to use a pure article, but this is not 
always obtainable, so to be sure of having a pure product the 
safest course is to make it. This is easily done, as pure caus- 
tic potash can be readily obtained. A good soap can be made, 
even with crude appliances, according to the following form- 
ula: Put 224 lb. of red oil in a kettle and heat it to 100° F. ; 
then run in slowly, with constant stirring, 10| gallons of solu- 



442 PRACTICAL TANNING 

tion of caustic potash of 60° Twaddell. Allow to stand 24 
hours and the soap is ready for use. 

Oiling chrome leather. — The finishing of chrome leather 
cannot be called currying, as no heavy stuffing or hard grease 
is used, the only grease the leather receives being an emulsion 
of oil, soap, and degras, or some other suitable material, and 
a coat of oil applied to the grain before it is dried. The oils 
used for oiling the grain of chrome leather are neat's foot, 
olive, sperm, sulphonated, and paraffin. Neat's foot is often 
used alone as well as mixed with paraffin oil. A good mix- 
ture for chrome glazed leather is 1 part neat's foot and 3 
parts paraffin oils ; and for dull-finished leather equal parts. 
They should be warmed, mixed, and applied warm, the leather 
being well struck out with a slicker before it is oiled. 

Another good combination is 1 part olive oil and 3 parts 
paraffin oil. The mixture should be applied evenly over the 
grain, more being put on for a dull finish than for a glazed 
finish. It is best not to oil the flanks. Sperm and olive oils 
are good for colored leather. 

A pure petroleum oil, such as 34° gravity neutral, is suit- 
able for any glazed leather. Good results are obtained by 
mixing it with what is known as fleshing oil, using equal 
parts of the two oils. Heat the oils to 200° F., mix well, and 
let the mixture cool before it is used. 

To preserve the finish and prevent spewing, a coat of the 
petroleum oil heated to 100° F. should be applied to the leather 
after it is finished. The so-called finishing and kid oils are 
nothing but 34° neutral petroleum oils, although they are 
generally sold under fancy names at fancy prices. Fleshing 
oil is much cheaper than neat's foot, and produces equally 
good results. 

The paraffin oils, when used together with pure cod oil in 
proper proportions, are satisfactory for sole and rough leathers. 
The proportions of the two oils should be 25 to 60 per cent 
paraffin and 40 to 75 per cent cod; a good mixture is 60 and 
40, respectively. The regular 28° paraffin oil is the most suit- 
able for rough and sole leathers. 



FAT-LIQUORING 443 

Sulphonated castor oil is also used after glazing and be- 
fore drying to prevent the leather from cracking and oxidiz- 
ing in the air. In this case it is sufficient to apply a light coat 
of sulphonated oil (50 per cent water) to the grain before 
drying. Some tanners prefer to use for this purpose a mix- 
ture of equal parts of sulphonated castor oil and a light- 
colored mineral oil. 

Specially treated oils, which have great softening proper- 
ties, preventing spew and gum, and do not discolor the most 
delicately colored leather, are also procurable. 

Low grade and impure oil should not be put on chrome 
leather, as such oil undergoes a process of decomposition in 
the leather, imparts a bad odor to it, and spews Out on the 
surface in the form of white scum, which is removed with 
difficulty. The quantity of oil applied to the grain is small, 
and it is advisable to use only the best grade for the purpose, 
the increased cost being not worth considering in view of the 
better quality of the finish. 

Waterproof filling for sole leather. — The following 
method of waterproofing and otherwise improving chrome- 
tanned and bark-tanned sole leather, was patented by William 
R. Smith and assigned to the Buffalo Leather Co., of Buffalo, 
N. Y. 

A bituminous composition is introduced into the leather by 
bringing the latter into contact therewith at a temperature high 
enough to render the composition thin and fluid, but not high 
enough to injure the leather. The maximum temperature var- 
ies with the kind of tannage, vegetable-tanned leather resisting 
a temperature of 150° F. and chrome-tanned up to about 200° 
F. To ensure proper impregnation, the leather should be free 
from oils, glucose, etc. It is best to treat the leather in a 
rotary tumbling drum. The fluid mixture and the heated soles 
are put into the drum, which is steam-jacketed and heated, 
so that the temperature of the air within it is somewhat above 
the melting point of the mixture. The drum is preferably pro- 
vided with radial inwardly projecting shelves adapted to raise 
and release the composition and the pieces of leather as the 



444 PRACTICAL TANNING 

machine rotates. The operation is continued until the com- 
position has thoroughly permeated the leather. Whole sides 
may be treated, but the inventor prefers, for economy of 
the mixture, to tumble the leather with the composition after 
it has been cut into forms or soles of the final size. The 
process is ordinarily completed within one-half hour. 

The bituminous composition used contains as its essential 
components a solid bitumen possessing a considerable degree 
of elasticity, combined with some other bitumen having 
marked penetrative powers. The variety of elastic bitumen 
preferred is elaterite or "mineral rubber," and the variety of 
penetrative bitumen is ozokerite, a "mineral wax." While the 
elaterite is greatly desired in such a composition, its use has 
been prevented by its infusible and insoluble character, also 
by its viscosity when brought into a state of fusion by ad- 
mixture with other bitumens. This difficulty is overcome by 
altering the character of the elaterite so as to render it easily 
soluble in melted ozokerite or equivalent paraffin. When elat- 
erite is gradually added to a melted bitumen, such as gilsonite, 
which is capable of withstanding a high degree of heat with- 
out decomposition, it is softened and gradually dissolved, and 
thus an infinitely large quantity can be melted in the presence 
of a small amount of gilsonite. The elaterite, fusible at high 
temperature without decomposition and soluble in hot paraf- 
fins and forming therewith a thin, penetrating liquid, is herein 
termed "modified elaterite." 

An example of modified elaterite is the so-called "kapak," 
a bitumen well-known in the trade and produced from elat- 
erite. The elaterite found in Utah (ozokerite also comes from 
that State) has all the desired qualities for this process. It is 
non-friable, tenacious, only moderately brittle at low tempera- 
tures, elastic at normal temperatures, resilient, and resistent 
to chemical alteration. When slightly warmed it becomes 
more flexible and more elastic so that if drawn out or bent — 
like rubber — it tends to return to its former shape upon re- 
lease. It may, by fusion with a solid paraffin body, be brought 
partly into solution, but it is preferable to render it substan- 



FAT-LIQUORING 4-45 

tially soluble in melted solid paraffin by previous modification. 
Ozokerite, having a higher melting point than ordinary solid 
paraffin, is found to be a superior ingredient in this special 
composition. The proportion of paraffin to modified elaterite 
naturally varies somewhat according to the specific qualities 
given the latter, 3 parts of ozokerite to 1 of modified elaterite 
being generally suitable. 

The flexibility and resiliency of elaterite are found to be 
measurably retained by the composition, and in addition, it 
possesses a surface frictional resistance such as is possessed 
by beeswax. The value of this latter quality is clearly ob- 
served when chrome-tanned sole leather is worked through 
this process. Notwithstanding the durable character of chrome 
leather, its use for the soles of shoes has been greatly limited 
by its slippery nature in wet weather. When chrome leather 
is impregnated with the composition by this process, this un- 
desirable quality is effectually overcome. The wearing qual- 
ity of heavy leather of all kinds for use as soles and heels 
is greatly increased by this treatment. When finished leather 
filled with ordinary paraffin wax is placed in hot sunshine or 
near a stove there is a strong tendency for the wax to melt 
and exude, thus defacing the shoe or other article. On ac- 
count of the viscosity and high melting point of the composi- 
tion used in this process the leather is not injured by any 
similar rise in temperature. 

Another combination, which is not patented, consists of a 
mixture of 50 parts paraffin wax, 25 parts of rosin, and 25 
parts of carnauba wax. 

Stuffing chrome lace leather. — After the stock has been 
tanned, neutralized, and washed in the usual way, it should 
be placed in a hydraulic press, or run through a Quirin 
wringer to take out the excess moisture. It should be run 
in a dry mill to take out all the wrinkles, and then allowed to 
sammie to contain approximately 40 per cent of moisture, tak- 
ing great care to prevent any portions of the hide from be- 
coming dry and eventually dark when stuffed with grease. 

When the leather has been properly sammied, it should 



446 PRACTICAL TANNING 

be weighed, placed in the stuffing drum which has been pre- 
viously heated to 180° F., and allowed to run for about 5 
minutes so as to open up and become heated through. Then 
add to the drum for each 100 lb. of stock 10 lb. of oleo-stear- 
ine substitute and 3 lb. of No. 3 "setine," melted together at 
a temperature of 150° F. Run for about 30 minutes, or until 
all of the grease is well taken up. The leather is then removed 
from the drum and hung on hooks until the grease has set 
and the stock is perfectly cold. This permits the leather to 
absorb the grease so that no excess is left on the flesh and 
grain. 

The stock should then be placed in clean water at not over 
90° F., and should remain in this water for about 10 minutes, 
or until the fiber has taken sufficient water to set out easily. 

It should then be taken from the water, placed on the table 
and struck out on the flesh with a slicker ; then turned over, 
set out perfectly on the grain, and oiled off with No. 3 setine, 
giving a fairly liberal coat along the back and over the hips, 
and a light coat over the balance of the hide. The stock 
should then be hung up from head to tail until the oil has sunk 
in from the surface. It should then be tacked out and dried in 
the usual way, after which it should be sammied with water, 
or preferably in sawdust, staked, and finished. 

Shaving the flesh lightly on the machine decidedly improves 
its appearance, after which the grain should be glassed by 
hand and then a light coat of talc put on with a brush and 
well rubbed in and the excess wiped off with a woolen cloth. 

Each of the above products is pure white and assimilates 
perfectly with the moisture in the leather. They will not 
oxidize, nor will they react with the chromium salts. 

The proportions recommended must necessarily be varied to 
meet requirements. If the leather is inclined to be soft, oleo- 
stearine substitute alone may be used to advantage, using only 
the No. 3 setine to oil off after setting, so as to mellow the 
stock along the back and over the hips. 



CHAPTER XV 
FINISHING LEATHER 

In the previous chapters have been described the various 
processes employed for treating hides and skins. Rather than 
carry each kind of leather through the final finishing process 




Figure 97. — Exterior view of Proctor dryer. 

it has been thought best to bring them to a point where the 
final operations of producing a marketable product become 
necessary. Thus we have studied beam-house methods, tan- 
ning processes, coloring and fat-liquoring, and now we will 
consider the application of various seasonings and the me- 
chanical operations necessary to produce the desired results. 
Setting-out. — For practically all classes of leather the stock 
is set-out after fat-liquoring. This is done on machines or 
may be set by hand on a smooth-top table. In any case, the 

447 



448 PRACTICAL TANNING 

idea is to smooth out the leather and free it from excess of 
liquor. 

Drying. — The skins or hides having been set-out are next 
dried. This is usually done by hanging the stock in a dry 
loft. Skins are, as a rule, suspended by the butt, while sides 
are suspended by the butt and neck. The conditions of the 
dry loft vary greatly with the kinds of stock, but, as a rule, 



1 

" ■&■■■ —**m ' * ' "*■"" 

m ' " 1 -— - f ■ Pk9v 

- ', ■ i, '■ . .... • ; ; '; . ...' > 



Figure 98. — Skins entering at the "wet end" of Proctor dryer. 

it may be said that vegetable-tanned stock should dry slowly, 
while chrome-tanned stock will stand a higher degree of heat 
in the loft. For chrome-tanned stock several forms of rapid 
mechanical dryers are employed, the most common being 
known as the Proctor dryer, shown in figures 97, 98, and 99. 
In the ordinary dry loft the skins are suspended from hooks 
or over sticks (figure 100), and the temperature regulated by 
means of steam coils passing under a grating on the floor. 
To ensure a proper circulation of air, most dry lofts are pro- 
vided with fans of the blower type, which may be used either 



FINISHING LEATHER 



449 



to blow the air into the loft, or may be placed so as to draw 
off the moisture-laden air. This method is best shown in 
figures 101, 102, 103, 104, and 105. 

The drying tunnel has been found to give exceptionally 
good results on chrome leather. This consists of a long nar- 
row tunnel on each side of which is an endless conveyor, both 
the Proctor and Sturtevant being types of such equipment. 
The damp stock enters the cool end and gradually approaches 




Figure 99.— Skins leaving the "dry end" of Proctor dryer. 

the hot end of the dryer from which it is removed when in 
the proper condition. 

Dampening. — After the leather has been dried out, in order 
to set the fiber it must again be dampened back or sammied 
before carrying out the finishing processes. Two methods 
of dampening leather are employed, the first consisting of 
dipping the stock in warm water, and then packing down in 
pits over night; and the second in placing the leather in piles 
with damp sawdust between each skin, and then covering the 
pile completely with more damp sawdust. By either of these 
methods the stock becomes uniformly damp without contain- 
ing an excess of moisture in any part. 



450 



PRACTICAL TANNING 



Staking. — When the leather is in a properly sammied condi- 
tion it is ready for stretching or softening, which is done in 
several ways. The most common method of stretching is 
accomplished by working the skin or sides on a staking ma- 
chine, illustrations of which are shown in figures 106, 107, and 
108. The leather is placed on the bed of the machine, and is 
then held in position while the jaws close in, and on retreat- 




Figure 100. — Interior of a typical dry-room in a goatskin tannery. 
The room is heated by steam pipes on the floor and ventilated 
by means of fans. 

ing impart a pulling and breaking effect. In place of ma- 
chine staking, an older method consists in working the skins 
over a blunt knife, pressure being applied by placing the knee 
in the fold of the leather and drawing downward. This is 
known as knee-staking, and is illustrated in the chapter on 
Alum Tanning. Leather is also softened and stretched by 
means of the moon knife, which gets its name from its pecu- 
liar shape. This method of staking is spoken of as "perching." 
Buffing. — When it is desirable to produce a velvety appear- 
ance on the flesh side of the leather, the dry skins are passed 



FINISHING LEATHER 



451 



over a carborundum or emery wheel, as shown in figure 109. 
This is sometimes done while the stock is still wet, in which 
case a carborundum stone is used, known as a "wet wheel." 

Tacking. — To conserve as much measurement as possible 
and produce a smooth piece of leather the stock is usually 
tacked. This is done by placing the sammied and staked 
leather on a frame and tacking around the edge. In carrying 
out the operation the skin is placed flat on the board and 




Figure 101. — Side view of Sturtevant dryer showing supply pipe, 
heater and open tube. 

several tacks are placed in the butt. The neck is then pulled 
tight and tacked in position. Tacks are then driven along 
the sides, two men usually working on one skin on opposite 
sides. The care taken in this operation has a great influence 
on the finished product. When tacked, the stock is allowed 
to dry. 

Stripping. — When thoroughly dry on the boards the tacks 
are withdrawn, or what is known in the trade as "stripped." 

Seasoning. — On removal of the skins or sides from the 
boards they are ready for the application of the seasoning 
solutions. These vary, and may be applied by hand, with a 



452 PRACTICAL TANNING 

brush, or on the seasoning machine. Some finishes require 
only one application, while others may require a number. 

Rolling. — For semi-bright leather the stock is usually 
worked on a rolling-jack. This machine consists of an arm to 
which a steel roll is attached. This roll, in playing on the bed 
of the machine, imparts a smooth surface to the leather with 




Figure 102.— Rear end of heaters, Sturtevant dryer, showing steam 
and drip connections. 

which it comes in contact. Patterns are also sometimes em- 
bossed on the roller. 

Glazing. — For leather which is to be finished with a high 
gloss the glazing-jack is used. This machine somewhat re- 
sembles the rolling-jack, except that the arm is provided with 
a glass cylinder which remains stationary, and in passing over 
the bed causes a certain amount of friction. The heat pro- 
duced thus imparts a bright polish to the leather. Two types 
of such machines are shown in figures 110 and 111, while a 
"line" in operation is shown in figure 112. 

Ironing. — When a dull finish is desired, the stock, in the 
case of chrome-tanned leather, is oiled and then ironed with 



FINISHING LEATHER " 453 

a hot flat iron. The same result may also be obtained on a 
smooth plate machine as described under embossing. 

Embossing. — When it is desired to impart an artificial grain 
to a leather it is placed between the plates of an embossing 
machine. These machines are capable of great pressure, and 
may be used for smooth-plating or embossing as desired. 
Such machines are shown in a previous chapter. 




Figure 103.— Sturtevant leather dryer, double tube, showing drying 

trucks. 

Boarding.— For some finishes, and when a soft leather is 
required, it is customary to work the rolled, glazed, or em- 
bossed stock on the table with an arm board. By the fold- 
ing action thus produced the grain is raised and various ef- 
fects are obtained. 

Measuring.— As all light leather is sold by the square foot, 
it becomes necessary to take measurements. Several ma- 
chines are on the market for this purpose, but they all work 
on the same principle. Figure 113 illustrates a Turner meas- 
uring machine. 

Sorting.— The skins are sorted and made ready for market 
as shown in figure 114. 

Having briefly outlined the steps employed in finishing light 



454 PRACTICAL TANNING 

leather we will now notice their application to the various 
kinds and grades of leather. 

Finishing chrome-tanned sheepskins. — After chrome- 
tanned sheepskins have been dyed and fat-liquored, they are 
struck out and the grain is oiled lightly with a mixture of 
1 part of neat's foot oil and 3 parts of paraffin oil for glazed 
finish, and equal parts of neat's foot and paraffin oils for dull 



Figure 104. — End of two tubes of Sturtevant dryer, showing skins 
hanging from chain belt-conveyor. 

finish. Care must be taken not to give the skins too much fat- 
liquor as this makes them too soft and spongy. After the 
grain has been oiled the skins are hung up to dry. The best 
results are obtained from rather slow drying in a room with 
a temperature of about 80° F., and having a good circula- 
tion of air. 

When dry, the skins are dampened Imd staked. A satis- 
factory way to dampen them is to put about a dozen skins 
into a tub two-thirds full of water, leaving them two or 
three minutes therein, then placing them in a well-covered 
pile on the floor or in a box. When they have become pli- 
able they are staked and re-staked, and then tacked on boards 



FINISHING LEATHER 



455 



to dry. When thoroughly dry, they are taken off the boards, 
trimmed, and prepared for the work of finishing. 

Black glased finish. — Where the. grain of the leather is 
greasy, it is advisable to apply a dilute solution of acid to 
clear it. Either lactic or formic acid may be used. The 
acid, diluted with water, is rubbed into the grain and the 
leather is dried. Then the grain should be rubbed with a 




Figure 105.— Looking into the end of Sturtevant leather dryer, show- 
ing skins on conveyor. 

soft cloth and given the first coat of seasoning. The acid as- 
sists in getting a clear, bright finish. 

An excellent seasoning for black-glazed finish is made of 
the following ingredients : ivory soap, 1 lb. ; glue, 1 lb. ; log- 
wood crystals, 3 oz. ; nigrosine, 4 oz. ; potassium dichromate, 
| oz. ; fresh beef blood, 2 quarts. 

Dissolve the soap and glue each in 8 gallons of boiling 
water; dissolve the logwood and nigrosine in 2 gallons of 
hot water, and add the dichromate ; when cold, add the blood. 
Take 1 quart of the glue solution and 1 quart of soap solu- 
tion, and mix into the logwood and blood solution; stir well 
and strain. Rub a light coat of this seasoning into the grain 



456 



PRACTICAL TANNING 



of the leather. Dry in a warm room and glaze. Apply a 
second coat of seasoning, dry, and glaze again. Finally, after 
the finish has aged a little, oil it very lightly with warm fin- 
ishing oil or with a mixture of equal parts of neat's foot and 
paraffin oils. 

The following formula also produces an excellent season- 
ing for glazed finish : whole flaxseed, 2 oz. ; logwood crystals, 




Figure 106. — Standard staking machine. 

2 oz. ; nigrosine, 2 oz. ; potassium dichromate, ^ oz. ; blood, 
1 quart; glycerine, \ pint; and carbolic acid crystals, 1 oz. 

Boil the flaxseed 30 minutes in 1 gallon of water; then 
strain the solution and add the logwood, nigrosine, and di- 
chromate and boil again; then cool the solution to 90° F., and 
stir in the blood, glycerine, and carbolic acid. There should 
be 2 gallons of seasoning. If there is less, add enough cold 
water to make the quantity specified. Apply the dressing to 
the skins, dry, and glaze in the usual manner. 

Another formula for glazed finish is : blood albumen, 1 lb. ; 
black nigrosine, 5 oz. ; logwood crystals, 1 oz. ; and denatured 
alcohol, | pint. 



FINISHING LEATHER 



457 



Dissolve the blood albumen by standing over night in 1 
quart of water. Boil the nigrosine and logwood in 3 gallons 
of water. When the solution is cold, add the albumen and 
alcohol. Give the skins two coats of this seasoning, and glaze 
them twice. 

When the grain of the leather is greasy, it is best to rub 




Figure 107.— Staking, or softening and stretching the damp stock. 

in a solution of alcohol and black nigrosine. Dissolve 1 oz. 
of nigrosine in 1 gallon of water and add a little alcohol. 
Rub this into the grain of the skins, and apply the seasoning 
when dry. The black is deepened by this treatment and the 
grain is cleared. 

A solution of oil-soluble nigrosine in benzine is beneficial 
in touching up spots which are not a good black. 

A kid finish on black sheepskins can be secured by the use 
of the following seasoning: logwood liquor, 6 quarts; beef 
blood, 2 quarts; orchil, \ pint; water, 1 quart; ammonia, \ 
pint; and milk, \ pint. 

There are excellent seasonings on the market, so the tanner 



•158 



PRACTICAL TANNING 



can buy them and dispense with the labor of making his own 
finishes. This is done by many, who find it convenient and 
advantageous. 

Seasoning for dull finish. — The following is a good prescrip- 
tion : ivory soap, 1 lb. ; flaxseed, -| lb. ; beeswax. 4 oz. ; black 
nigrosine, 4 oz. ; gelatine, 4 oz. ; aloes, 2 oz. ; and denatured 
alcohol, | pint. Put the soap, flaxseed, and beeswax into 2 




Figure 108. — Perching goatskins, sometimes termed re-staking. 

gallons of water and boil 30 minutes, then add the nigrosine. 
Dissolve the gelatine in 1 quart of water and add to the solu- 
tion. Then dissolve the aloes in the alcohol, add to the other 
solution, and strain the mixture. Apply a coat of this dressing 
to the grain of the leather, rubbing it in well. When it is 
dry, iron the leather, and then give it a second dressing, but 
do not iron it again. As a finishing touch, oil the grain with 
paraffin oil. 

Seasoning for colored sheepskins. — 1. A clear, bright fin- 
ish is obtained on colored sheepskins by using a seasoning 
made of 4 gallons of egg-albumen solution, 1 oz. of potassium 



FINISHING LEATHER 



459 



dichromate, 2 quarts of acetic acid, and 20 gallons of water. 
The ingredients should be mixed thoroughly. The seasoning 
should be applied sparingly so that the grain and wool pits 
will show when the leather is glazed. 

A glazed finish is obtained on russet and colored leather 
by using the following dressing: Dissolve 4 oz. of blood albu- 




Figure 109. — Buffing room in a goatskin tannery. 

men by standing over night in 1 gallon of water; cook 4 oz. 
of granulated gelatin in 1 gallon of water and let it cool ; mix 
I pint of white shellac varnish with \ pint of ammonia; mix 
the three solutions thoroughly, add enough water to make 
three gallons, apply to the skins with a sponge, and glaze 
when dry. For colored skins, use a little less ammonia and 
make the finish a week before it is to be used, so that the 
ammonia will evaporate. For a plain natural finish, give the 
leather two coats of finish and roll it while it is wet, hang 
it up to dry, and then give it another coat of dressing. Boil 
1 lb. of flaxseed for some time with 3^ gallons of water. 
Strain the solution before using it, and beat it up the same 



460 



PRACTICAL TANNING 



as the white of an egg. To a pail of water add 1^ pints of 
milk, the whites of two eggs well beaten, and |- pint of flax- 
seed liquor also well beaten up. This finish should be put on 
evenly and without streaks by means of a soft sponge or a 
sheepskin pad. When it has been put on, the skins are hung- 
up to dry and then rolled. 

If embossed leather is required, the skins should be sea- 




Figure 110. — Bower glazing machine. 

soned and then embossed by an embossing machine. Imita- 
tions of seal, monkey, alligator, and other skins are made in 
this way. Beautiful effects are produced when the leather 
has been properly tanned and colored. 

Finish for embossed sheepskins. — These skins, tanned by a 
vegetable process, and to be grained or embossed, can be sea- 
soned with the following finish: 2 oz. of casein; 2 oz. of 
orange shellac ; f oz. ammonia ; and 1 gallon of water. Let 
stand over night, or until solution is complete. Add 1 gallon 
of water and \ oz. of glycerine, mixing all together. Apply 



FINISHING LEATHER 



461 



with a sponge, and dry. The skins are then ready for glassing 
on the machine. After glassing, they may be grained by arm 
board and embossed, which is the final operation. 

Finish for black embossed sheepskins. — A lasting finish is 
obtained by using this dressing on skins that are to be printed, 
grained, pebbled, or embossed. Put 8 oz. of extract of log- 
Wood, 1 oz. of potassium dichromate and 2 oz. of prussiate 
of potash in 2 gallons of water, and boil until dissolved; cool, 




Figure 111. — Flat bed glazing machine. 

and strain. To each gallon of the solution add either 2 quarts 
of beef blood or blood albumen. Give the skins an even coat 
of this dressing and let them dry. When the leather is ready 
to be printed or embossed, dampen the grain evenly so that 
it will take the impression without the grain being cut. Then 
print, grain, emboss or pebble according to the grain desired. 
Skins may be embossed in a dry state on a modern embossing 
machine, although a certain amount of heat is used to make 
the impression easier and more permanent. 

On some kinds of embossed leather it is desirable to have 



462 



PRACTICAL TANNING 



the crevices of the grain a lighter shade than the upper sur- 
face, which gives the leather a shaded appearance. To obtain 
this effect, the skins should be embossed first, and then col- 
ored by hand on the table. This not only produces the desired 
appearance as regards color, but also leaves the flesh clean 
and uncolored. East India skins are nicely colored this way. 




Figure 112. — A line of glazing-jacks for producing a bright finish on 

glazed kid. 

When skins are colored first and then dried and embossed, 
the plate of the machine should be large enough to cover an 
entire skin, so that there .will be no plate marks on either the 
flesh or grain side. To keep the flesh smooth and free from 
plate marks a thick piece of cowhide split should be spread 
over the bottom bed of the machine. The skins to be em- 
bossed are placed grain side up on this split. The plate then 
comes down on the grain and embosses it, while the flesh side 
remains smooth. Before embossing, the grain must be sea- 
soned and glazed with considerable pressure, so that it will be 
flattened out and smooth. Two or three glazings are gener- 



FINISHING LEATHER 463 

ally needed to get the right finish. When a sort of crushed 
or wrinkled grain is desired, strong tan liquor is used, which 
contracts the grain. Embossing is generally more satisfac- 
tory, as it produces a more uniform result. 

Very thin fancy leather is obtained by boarding or emboss- 
ing plump skins and then splitting them. The grain should 




Figure 113. — Segment measuring machine. 

be diced by rolling with a diced roller and then hand-boarded. 
The flesh splits are finished into ooze leather. 

De-greasing sheepskins. — As already stated, much of the 
natural grease in sheepskins can be removed by pressing in 
a hydraulic press previous to tanning, or while the goods are 
in the limed or the pickled condition, preferably the latter. 
Pressing before tanning is always advisable, yet this method 
is not always as effectual as might be desired, especially when 
colored leather is to be produced. Treatment with naphtha in 
liquid or gaseous form is therefore often resorted to. This 
method of de-greasing usually removes every particle of grease 
and oil from the leather. It is used after the tanned skins 



464 PRACTICAL TANNING 

have been dried and before they are finished. The work of 
de-greasing with naphtha should be done in a building apart 
from the main factory, and no fire or open light should be 
allowed near the naphtha vats. 

The skins are immersed in the naphtha in a tank or closed 
vessel or drum, which either revolves or in which they can 




Figure 114. — Sorting finished skins. 

be stirred or otherwise agitated to ensure rapid and thorough 
permeation of the naphtha. By processing the greasy leather 
in this manner the liquid becomes so thoroughly saturated 
with the oily matter extracted that it will take up no more. 
If one bath is not sufficient to extract all of the grease, the 
skins are removed to a fresh bath. They may be repeatedly 
subjected to a fresh supply of naphtha, until the liquid in 
which they are last placed remains pure and shows no trace of 
oil or grease. The action of the naphtha is harmless, and no 
strength of the leather is lost by this treatment. The leather 
can be de-greased by soaking it in the fluid for several hours 
and then pressing out the naphtha with a slicker. On a 



FINISHING LEATHER 465 

small scale, the work can be done by throwing the skins in 
loosely and separately, and stirring them about for an hour 
or two. Light skins show a difference after they have been 
in the liquid a half -hour. When they seem sufficiently de- 
greased they should be taken from the naphtha, pressed out 
with a slicker, and then hung up until the naphtha is entirely 
evaporated. 

Finish for India-tanned leather. — India-tanned skins are 
finished in various ways. Large quantities are finished in 
smooth glaze and dull; some are grained with a roller or em- 
bossed and then boarded up by hand ; and others are glazed 
and grained. For some purposes, such as bags, belts, etc., 
they are hand-grained three ways, which gives a round and 
half-round grain. To get a diced grain, the skins are rolled 
with a straight grain roller and then grained crosswise; after 
this they are boarded up, which softens them and produces a 
uniform grain similar to the box grain. Some skins are peb- 
bled and then boarded. The finish depends upon the purpose 
for which the leather is to be used. 

Black glased finish. — The skins, after they have been staked, 
are in condition to be finished. Seasoning for glazed finish 
is applied and rubbed into the grain. The skins are then 
dried in a warm room and glazed. A second coat of season- 
ing is then applied, dried and glazed. Sometimes it is advis- 
able to stake the skins again after the first staking and be- 
fore the second application of seasoning. 

Smooth dull finish. — A fine dull finish and soft, full skins 
are obtained by giving them after staking a coat of dull dress- 
ing, drying and ironing, after which they are staked lightly. 

Finish for colored skins. — An egg-albumen solution pro- 
duces a fine glazed finish. Apply with a sponge and glaze 
when it is dry. Egg-albumen is used for light shades, and 
blood albumen for dark shades. 

Re-tanning with chrome liquor. — Soft, durable leather is 
made by re-tanning India-tanned skins with one-bath chrome 
liquor. The skins are first sorted and all superfluous parts 
trimmed off; they are then soaked and shaved. After shav- 



466 PRACTICAL TANNING 

ing, they are washed thoroughly, drained a few hours, and 
then re-tanned with chrome liquor. Any good one-bath liquor 
may be used. A stain can be added to the liquor, and re- 
tanning and staining performed in one operation. When the 
re-tanning is completed the leather is washed, pressed or 
struck out, dyed, dried, and finished. 

Morocco finish. — There are three different ways of giving 
the leather a grain or the "morocco finish," as it is called. The 
best way is by graining it up naturally without giving it any 
false grain. This is done by a cork board when the skin is 
wet. The grain of the skin is turned to the grain and 
pushed backward and forward in eight ways, turning the 
skin each time. This method throws up a beautiful grain 
and makes a regular morocco figure. Heavy skins throw up 
a large grain, while the grain of light skins is fine and small. 
To hold this grain the skins are hung in a hot room to dry. 
This, of course, makes them hard and stiff, and it is neces- 
sary to go through the same work again, only with the skin 
dry instead of wet. This method keeps the former grain and 
makes the leather soft and pliable. 

Another good way, where prices enter into the question, 
is to take the skins from the dry room, wet them and put 
them under a jig roll. This is a small steel roll about 6 inches 
long, cut with indentations, so that the roll under great pres- 
sure on wet leather gives a pebbled or morocco figure. This 
also must be dried in, then wet down, and hand-grained just 
as the natural grain skin. This gives a beautiful regular 
morocco grain which will not pull out or flatten; and it is 
done without deterioration to the leather itself. 

The least desirable way, though much used, and really the 
best known among bookbinders, is embossing. The objec- 
tionable feature to this process is that, to keep the figure in, 
it is necessary to use heat. This injures the fibers and the 
grain, leaving the leather with an unnatural grain. No good 
work should be embossed. The process is most suitable for 
sheepskins or other skins when no other method will do, or 
else for any poor stock which cannot be finished in any other 



FINISHING LEATHER * 467 

way. The grain can be made bright by glazing at any time 
during these processes. 

The leather is next split. The grains are used for book- 
binding and other purposes, while the splits are made into ooze 
stock, which is used for pillows, linings, covering handles of 
golf sticks, etc. 

Crushed Levant grain. — This is obtained by embossing, then 
seasoning and glazing to flatten out the grain. Two or three 
glazings are needed to get the desired finish. The colors are 
generally blue, red, green, brown, tan, and wine. To get the 
best results in coloring it is advisable to emboss the skins and 
color them on the table, this giving the crevices of the grain a 
lighter hue than the upper surface, besides leaving the flesh 
clean and white. 

Plump leather always takes a good grain in boarding. For 
boarded grains it is best to roll them with a diced or straight 
grain roller. Should the latter be used, the skin should be 
rolled diagonally to form a small diamond, and afterwards 
hand boarded. The leather, if sufficiently plump, can be split 
so that the grain will be of the desired weight. The grains 
finished as described are used for collar and cuff-boxes, belts, 
hand-bags, pocketbooks, music rolls, etc. 

Ooze or suede leather. — India-tanned skins having defective 
grain can be made into ooze or flesh-finished leather more 
profitably than into other grades. Softness and good color 
are the essential qualities, as well as a short, smooth nap. 

The following describes the methods used in finishing India- 
tanned ooze leather : The skins are sorted, and those having 
good grain are colored and finished on the grain; while those 
having poor grain are thrown aside for ooze finish. The im- 
perfect skins are thoroughly washed and cleansed of dirt and 
surplus tanning material, struck out to rid them of surplus 
water and snuffed on the wet wheel. 

The next process is re-tanning with sumac, which not only 
re-tans the skins, but also prepares them for coloring. The 
sumac is applied in a warm solution in a drum, and the skins 
are then colored. Coloring is usually done in a drum, the 



468 PRACTICAL TANNING 

tumbling and pounding being necessary to carry the color into 
the leather. After the skins are colored they are fat-liquored, 
dried, staked, and rolled. 

Finishing skivers. — The work under this heading covers 
a large assortment of grains, rolled or embossed, as well as 
glazed. After the skins have been fluffed lightly, if required, 
they should be given a coat of Irish moss solution on the 
flesh, this having the effect of making them feel firm and 
stout. A practical way of making up the moss mucilage is 
by boiling gently equal parts by volume of Irish moss and 
water for about two hours, after which the solution is care- 
fully strained. When it is cold, it is ready for use. 

A coat of moss is applied to the flesh side, and the skivers 
are slowly dried out. The flaming, or filling of the grain, 
follows, the solution for this purpose being made from 10 oz. 
of liquid blood albumen, 1 oz. of milk, and 1 quart of water. 
Apply liberally with a brush, as this class of skivers requires 
considerable nourishing. A suitable seasoning is then applied 
with a pad. 

At this stage the skivers are laid under damp blankets for 
not less than 12 hours, when they are ready for the machine 
work. If the goods are for long grains they should be first 
well rolled with a dull roller — either a No. 4 or 5 — from belly 
to belly, two or three times if necessary, taking care to bring up 
a good color. Next break the skins down on the flesh side, 
with a hand board covered with rubber, air off and then glaze 
carefully. This has the effect of giving them a good level 
face and also flattens the roller work. 

The skivers are now embossed on the plate machine with 
whatever grain is desired. If, however, the goods are for 
straight grains, they should be first rolled with a No. 7 size 
roller, lightly boarded on the flesh, and then cut through with 
a No. 4 to separate the "oat" which has been made by the 
No. 7 roller, and finally lightly finished off on the glazing ma- 
chine. Goods for cross-grains should be rolled on the cross 
with a No. 5, boarded on the flesh, well glazed, and then 
boarded again on the grain. For plain glazed skivers great 



FINISHING LEATHER - 469 

care should be taken in glazing, no matter what class of ma- 
chine they are to be glazed on; it should be in perfect condi- 
tion and should have a good level stroke. Too much pressure 
must not be used, otherwise the goods will be very brittle, and 
it will be difficult to finish without tearing. Such goods should 
be well glazed, aired off with a little heat if possible, and then 
lightly drummed. 

For glace embossed skiver grains, only the stoutest skivers 
should be selected; those showing ribby marks should be re- 
jected. Skins showing rough flesh should be cleaned up by 
a light fluffing on the wheel, care being taken that the carbo- 
rundum or emery wheel is not rough enough to leave marks. 
Then give the skivers a good coat of Irish moss solution of 
about the same strength as that for flat finishing. Next fill 
in with a solution composed of 8 oz. of liquid blood albumen, 
1 oz. of milk, and 1 quart of water, adding a little color solu- 
tion if desired. 

The goods are now dried slowly; if dried too rapidly they 
will be harsh and liable to crack. When dry, they can be 
broken down on the flesh side with the rubber-faced hand 
board, and placed between damp sacks for about an hour, 
when they are ready for embossing to the grain required. In 
the embossing, the impression of the print is, of course, left 
on the flesh side; or, to be exact, the impression on the grain 
side is, of course, raised up on the flesh side, and vice versa. 
By running the fluffing wheel lightly over the flesh side it only 
touches the skin where the raised parts are ; consequently this 
part of the skin is left a little thinner, and the glazing tool 
cannot get to the .bottom of these parts, being held by the 
raised parts of the print. The friction caused by glazing 
darkens the goods or brings out the color, the result being 
a lighter shade between the scales and what appears a much 
more natural grain. The skivers are now ready for season- 
ing and the final work of finishing. There are great possi- 
bilities in this class of work, as frequently there is a fresh 
design on the market, while there is a constant and increasing 
demand for both' glazed and plain embossed skivers. The 



4.70 PRACTICAL TANNING 

above notes on the finishing of skivers is taken from 77: j 
Leather World. 

Seasoning for chrome calfskins. — After the skins have 
been trimmed, apply a coat of finishing seasoning, dry, and 
finish. Make the seasoning of 1| lb. of ivory soap, 3 oz. of 
French gelatin©, and 3 oz. of blood albumen. 

Shave the soap into 6 quarts of water and boil until dis-. 
solved. Dissolve the gelatine in 1 quart of hot water. When 
both solutions have cooled, mix, and stir them together. Soak 
the blood albumen over night in 2 quarts of water at 90° F. 
In the morning stir the soap into it. Strain a quart of the 
finish into 6 quarts of warm water. Apply a coat of the dress- 
ing to the leather, allow it to dry, then stake lightly and give 
a second application, and dry again. When the leather is 
still somewhat moist, roll it; then dry and jack it lightly, using 
a piece of hard felt instead of the glass. The pressure must 
be light, or the leather will show shaded spots. 

Bright finish, smooth or boarded. — This is obtained in the 
following manner : Apply to the staked and trimmed leather a 
coat of seasoning for glazed finish, and when it is dry, glaze 
under moderate pressure. Then put on a coat of finishing oil 
and iron the leather. A second coat of glaze seasoning is then 
applied, and after it is dry, the leather is glazed again. This 
gives a popular and smooth finish. If a box grain is desired, 
board the skins after the second glazing. 

Glazed finish. — When the leather has a clean, dry grain it 
is not difficult to get a good bright finish, and only a little 
seasoning or finishing solution is required. Such a finish can- 
not be secured where the grain is greasy, when too much sea- 
soning is applied, or when the pressure of the glazing machine 
is too high. 

A small quantity of ammonia or alcohol may be added to 
the seasoning to overcome oily grain, but either must be used 
sparingly or it will give a dry feel to the leather, and the fin- 
ish will fly off during glazing. Blood seasoning is satisfac- 
tory for ordinary glazed finish. Sponging the grain with a 
dilute solution of formic or lactic acid cuts surface grease. 



FINISHING LEATHER 471 

and when the grain has dried, the leather is in condition to be 
seasoned and finished. 

Give the grain an application of the seasoning, rubbing it in 
well. Hang the leather up to dry, and then glaze it. Next 
give a second coat of seasoning, dry, and stake the skins; then 
glaze them a second time. 

Seasoning for black glased finish. — Whole flaxseed, 2 oz. ; 
logwood crystals, 2 oz. ; nigrosine, 2 oz. ; potassium dichrom- 
ate, \ oz. ; vinette, \ pint; beef blood, 1 quart; glycerine, \ 
pint; and crystal carbolic acid, 1 ounce. 

Boil the flaxseed for a half-hour in a gallon of water, and 
then strain. Add the logwood, nigrosine, and dichromate. 
When the mixture has cooled to 90° F., add vinette, blood, 
glycerine and carbolic acid. Stir the mixture thoroughly, and 
if there is less than 2 gallons, add enough cold water to make 
it up to that amount. 

Boarded or box finish.— -The leather for boarded grain 
should be glazed and then grain-pressed. To obtain a sharp 
and regular grain it is best to press the leather before board- 
ing or graining it. A powerful press and sharp-cut rolls are 
required. The skins are boarded first from head to tail, then 
from side to side. The grain is then oiled the same as for 
smooth finish. 

Smooth dull finish. — Take the skins from the tacking 
frames and trim them. Apply a coat of dull dressing to the 
grain and let it dry; then give another coat and dry again. 
Finally, iron the leather with, a hot iron, then stake it. Fin- 
ished in this way the leather has a fine break and feel, and 
is soft and full. 

Where the grain is bad, a light snuffing is required to im- 
prove its appearance. Some finishers simply apply a coat of 
the dressing and allow it to dry. A coat of finishing oil is 
then applied and the leather is ironed. 

Seasoning for black dull finish. The same finish may be 
applied here as given under sheepskins. 

Gun-metal finish.— -To get this finish, after trimming, the 



472 PRACTICAL TANNING 

skins are glazed and staked. Next apply a coat of gum trag- 
acanth, 1 oz. ; yellow dyestuff, \ oz. ; and seasoning for glazed 
finish, 1 gallon ; after which dry and iron the leather, then oil 
the grain with hot oil. 

Soak the gum tragacanth for 24 hours in 2 quarts of water ; 
then stir it until it is dissolved. Dissolve the yellow dye in 
1 quart of water. Take 1 gallon of the seasoning for glazed 
finish and stir in 1 quart of the gum solution. Then add the 
solution of yellow dye, a little at a time, stirring thoroughly, 
until the color of the mixture has changed from black to 
greenish-black. Too much yellow dye must be avoided, other- 
wise the finish will be too green. For oiling off, after finish- 
ing, use a mixture of equal parts of paraffin and neat's foot, 
or any other good finishing oil. 

Finishing chrome goat leather. — The skins having been 
colored and fat-liquored, the next operation is setting out the 
grain of the leather by hand or on a machine, and applying 
a solution of glycerine in water — equal parts of each. The 
leather is then placed grain-to-grain over a horse and left for 
an hour or two. It is then set out again, somewhat harder 
than before, and given an application of oil on the grain. .The 
leather should be thoroughly set out, all wrinkles and marks 
of the tool removed, and the grain laid down flat and smooth. 
Any one of the following oils may then be used : Neat's 
foot, olive, sperm, or any other leather oil; mixtures of neat's 
foot and olive, or neat's foot and paraffin oils are good also. 
For instance, equal parts of- neat's foot and paraffin oils make 
a good oil for either dull or glazed finish. It is good prac- 
tice to apply the oil warm. The skins are next hung up to 
dry. Colored leather should be dried in a darkened room, 
while the drying of the black leather is effected most satis- 
factorily in a warm room provided with fans to keep the air 
in circulation. 

The dry leather should be kept in a clean, dry room until 
it is desired to finish it; it is then sammied and staked. 
Staking and drying should be continued until the skins are 
worked out dry and soft. It is well to stake the skins both 



FINISHING LEATHER 473 

ways on the machine. The necks and shanks are often staked 
by hand. 

To remove roughness from the flesh, the leather may be 
run on an emery wheel or on a buffing machine. It is then 
seasoned and finished. 

Clearing the grain from grease. — Dissolve 1 oz. of black 
nigrosine in 1 gallon of boiling water, and when the solu- 
tion is cold, add a small quantity of wood alcohol. Apply 
this to the grain of the leather, rubbing it in well, then ap- 
ply the seasoning for glazed finish. 

Blacking defective spots. — Oil-soluble black aniline, dis- 
solved in benzine, and applied with a sponge to spots which 
are not well blacked, dyes them at once and improves the color 
of the leather. 

Black glaze finish. — A brilliant black glazed finish can be 
obtained by using one of the seasonings prepared in accord- 
ance with the formulas given under sheepskins. The season- 
ing or finishing solution should be rubbed well into the grain, 
a light and uniform coat being applied. Two applications of 
seasoning are always required to get a good finish, and fre- 
quently it is advisable to apply a third coat. After the sea- 
soning has been applied, the skins are dried and glazed ; then 
the second coat is put on, the skins dried again and glazed, 
the operation sometimes being repeated four or five times. 

The finishing of glazed leather requires skill and care. The 
luster must be clear and bright and the grain well worked 
down. After glazing is completed, the leather receives a light 
application of finishing oil; it is then sorted into grades and 
tied up in bundles. 

Seasoning for colored leather. — The same methods as given 
under sheepskin and calfskin apply equally well to this class 
of stock. 

Dull finish. — When dull-finished leather is required, the 
skins are staked and trimmed, then given a coat of finish, 
dried, given another application of finish, dried again, and 
ironed with a hot iron. Heavy skins should be staked lightly 



474 PRACTICAL TANNING 

after ironing, which makes them softer and fuller than when 
this is not done. 

Finish for kangaroo leather. — The glazed and dull fin- 
ishes may be obtained by following the same procedure as 
given under goatskins. 

If colored kangaroo is desired, the instructions given for 
calfskins should be followed. 

Finishing chrome side leather. — After having been fat- 
liquored, the leather should be placed over horses to press 
and drain until the next day, and then thoroughly set out and 
oiled on the grain side. For glazed leather, use 1 part neat's 
foot oil and 3 parts paraffin oil, or equal parts of olive and 
paraffin oils, or treated cod oil, giving the grain a light appli- 
cation, and then hanging the leather up to dry. 

Dull-finished leather may be oiled with treated neat's foot 
or cod oil, with dull morocco dressing oil, or with a mixture 
of neat's foot and paraffin oils. The oil should be applied 
evenly over each piece of leather, and it is best to warm it be- 
fore using it. No oil should be put onto the flanks. After 
having been oiled, the leather should be hung up to dry in a 
room having a temperature of about 80° F., and there should 
be a good circulation of air so that it will not dry too rap- 
idly or have a parched appearance. When dry, it is sam- 
mied and staked, and after having been staked, it is tacked 
out smoothly and allowed to dry. It is then trimmed and sea- 
soned for finishing. 

Dull finish. — A coat of dull dressing is applied to the grain 
of the leather, and another coat is given when it is dry. The 
leather is next dried and ironed with a hot iron, then staked 
lightly. When well tanned and fat-liquored, the leather, fin- 
ished in this manner, is soft and full, and has a fine, tough 
grain. 

Glazed finish. — The leather is trimmed and staked, and 
given a coat of finish and dried. The next operation is glaz- 
ing. Then the leather is given another coat of finish, dried 
and staked, and glazed again. If the finish is satisfactory, a 
light coat of finishing oil, or a mixture of neat's foot and 



FINISHING LEATHER 475 

paraffin oil, is applied to preserve the finish. The leather 
not infrequently requires a third coat of finish and a third 
glazing to make it satisfactory. 

Boarded finish. — The leather is treated as for smooth glazed 
finish, and after the second glazing it is boarded from head 
to tail, then across from side to side, and oiled lightly. 

Dull English grain leather is given a coat of seasoning, 
dried, rolled on a heavy jack with heavy pressure, then 
grained and oiled heavily with a mixture of neat's foot and 
paraffin oils. To obtain a sharp and regular box grain, the 
leather is pressed with a powerful press and sharp-cut rolls 
before it is boarded. Boarding and oiling are the finishing- 
touches. 

Gun-metal finish. — This finish is secured by giving the 
leather a coat of bright seasoning, drying, glazing, and staking. 
A coat of the following finish is next applied, and when it is 
dry, the grain is ironed and oiled off with hot oil : gum 
tragacanth, 1 oz. ; yellow dye, 2 oz. ; and seasoning for glazed 
finish, 1 gallon. 

Storm-grain leather. — For chrome-tanned oil-grain or 
storm-grain leather the following formula makes a good 
finish : gelatine, | lb. ; nigrosine, 2 oz. ; olive oil, 1 pint ; and 
ammonia, \ pint. 

Dissolve the gelatine in 2 gallons of water; add the nigro- 
sine, and heat until gelatine and nigrosine are dissolved. Cool 
the mixture, and just before it begins to thicken, add the oil 
and ammonia, and stir thoroughly. After the leather has 
been seasoned and grained, oil the grain with a mixture of 
neat's foot and finishing oils, applied hot. Another finish 
suitable for heavy grain leather is made of \ lb. of green-olive 
soap, 1 quart of moellon degras, 4 oz. of Irish moss, 2 oz. of 
logwood crystals, and 2 oz. of nigrosine. 

Boil all together in 1 gallon of water for 20 minutes; cool, 
strain, and add water to make 2 gallons of finish. Apply this 
dressing liberally, and when the leather is half dry, roll it 
on a heavy jack, applying heavy pressure. Then grain the 
leather and oil off with hot oil. The leather should be rolled 



476 PRACTICAL TANNING 

while it is damp as this treatment produces a smoother grain 
and a more uniform break when graining. 

Finish for colored leather. — The same procedure should be 
followed as given under sheepskins and calfskins. 

Heavy chrome grain leather. — Heavy chrome leather made 
from the grains of split hides and from heavy calfskins is 
used in the manufacture of boots and shoes for sportsmen, 
etc. This leather is soft and waterproof, due to the chrome 
tannage and oils used in finishing it. The colors are black, 
tan, and chocolate. The leather is very durable and is well 
suited to such purposes. Hides to be made into this leather 
are split out of the limes, and the grains 'are then bated, 
pickled, and tanned in a one-bath chrome process. 

Fat-liquoring is done in the usual manner after the leather 
has been washed, neutralized, and shaved.' A good fat-liquor 
for 100 lb. of leather consists of 2 lb. of neat's foot oil, 2 lb. 
of soap and 1^ lb. of degras, thoroughly emulsified. The 
leather is drummed with this liquor for 40 minutes, and is 
then blacked by hand with logwood and striker, or with a 
direct chrome black. When a direct black is used, it is ad- 
visable to add a small quantity of gambier to the fat-liquor, 
or drum the leather in the gambier liquor before grain black- 
ing. Where it is desired to color both flesh and grain, the 
leather is drummed in the dye in the usual manner, but where 
the grain only is to be blacked, dyeing is done by hand or on 
a machine. After having been dyed, the leather is washed, 
set out, hung up, and partly dried. A heavy coat of oil is next 
applied to the grain to make it soft and waterproof. A thick 
fat-liquor emulsion may be used for this purpose, also sul- 
phonated oil in concentrated form. The grains are horsed-up, 
grain-to-grain, for 24 hours, and then hung on hooks by the 
hind shanks to dry. Little staking is necessary, particularly 
if the leather is staked while it is drying. 

If a boarded finish is desired, the leather is grained in two 
or three directions, and a finish consisting of soap, oil, bees- 
wax, and water — or a dull, oily dressing — is applied to the 
grain which is later on brushed, oiled again, and the stock is 



FINISHING LEATHER 477 

then sorted into grades. Printing or embossing with the box 
grain and then boarding the leather makes a fine grain which 
does not readily become smooth. For the shades of dark 
tan and brown, a mordant of gambier and fustic is used, 
coloring being effected with basic dyes. This is done best 
before the leather is fat-liquored, as grease applied before col- 
oring is likely to prevent penetration of the color into the 
goods. Smooth finish is obtained by ironing or rolling the 
leather before the seasoning is quite dry. Excellent colors 
are also obtained by using acid dyes and sodium bisulphate 
after the leather has been fat-liquored. 

Black chrome oil grain leather. — This leather is usually 
made from good plump hides weighing not over 50 lb. each 
green-salted weight. Splitting is done after liming, or after 
the sides have been tanned and pressed. In the latter case, 
re-tanning with chrome liquor is necessary. Neutralizing, 
washing, and shaving is done in the usual manner, and the 
leather is then blacked with hematin (logwood) crystals and 
direct chrome black; and after it has been washed and pressed 
it is ready to be fat-liquored. It is best to press the leather 
hard and then to put it into a dry mill and run for a half-hour. 
Before the fat-liquor is applied, the leather should be spread 
on a table, grain side up, and the flanks and bellies dampened 
so that they will not take as much grease as the remainder 
of the leather. 

The following quantities of grease in fat-liquoring are re- 
quired for 100 lb. of pressed leather: 8 lb. of stearine, 6 lb. 
of tallow, 2 lb. of degras, and 2 lb. of sod oil. These stuffing 
greases are put into a kettle and heated to 190 F. The 
leather is first run for 10 minutes in a hot drum, then given 
the hot grease and drummed 45 minutes, and 10 minutes with 
the door off. It is next piled in a box, covered up, and al- 
lowed to lie over night. The next morning it is struck out 
on the flesh side, then on the grain side, and hung up 5 or 
6 hours. It is then re-set on the grain side and tacked on 
frames to dry. In re-setting it is necessary to use a setting 
slush so that the leather will stick to the table. This is made 



478 PRACTICAL TANNING 

of 3 lb. of degras and 3 quarts of finishing oil, melted to- 
gether; then dissolve 1 lb. of soap in 1 gallon of water, and 
stir in the degras and finishing oil. Add enough cold water 
to make 6 gallons of the mixture. 

When dry on the frames, the leather is shaved lightly on 
the flesh side in the shaving machine, which gives a clean 
back. A clean, dry, and greaseless back is essential on this 
leather, as shoes made from it are frequently unlined. The 
leather is trimmed and staked, then boarded from back shank 
to neck and from front shank to tail, this making what is 
known as English grain. After it has been thus grained, the 
leather is given two coats of finish and hung up until the finish 
is dry. It is then measured and grained lightly, just enough 
pressure being applied to bring up the grain. The leather is 
now ready to be sorted and tied into bundles. 

Leather for sporting goods. — Chrome leather is used in the 
manufacture of sporting goods, such as punching-bags, foot- 
balls and baseball gloves. Light hides and kips work into 
this class of stock more profitably than larger or smaller 
skins. The flesh splits taken from the hides can be finished 
into cheap glove and mitten leather. 

After having been tanned, washed, and shaved, the leather 
is colored and fat-liquored. The use of sulphonated oil as a 
fat-liquor, or a mixture of it and neat's foot oil, is especially 
suitable for this leather. For the shades of color most in 
demand it is advisable to fat-liquor first and color afterwards. 

When dry, the leather is dampened, staked, and tacked out 
to dry. It is then trimmed, re-staked lightly, and put into 
a dry drum together with 5 lb. of talc for one dozen skins 
and drummed two hours. The grain is then brushed with a 
soft brush and the skins are measured and sorted. 

Finishing vegetable-tanned grains into black leather. — 
The goods after being fully tanned, are washed, struck out, 
shaved, and re-tanned with sumac at 90° F. The leather is 
put first into a sumac liquor which has been used for a pre- 
vious pack, and after 24 hours is placed in a new bath. It 
is then horsed-up, set-out, oiled on the grain with cod oil or 



FINISHING LEATHER 479 

other leather oil, hung in the air, struck out on the flesh, and 
fat-liquored on the flesh with a mixture of degras and cod 
oil, applied sparingly in order to avoid greasy grain. In place 
of this fat-liquor, the following may be used for 100 lb. of 
leather: 5 pints of cod oil, 5 pints of moellon degras, 5 lb. 
of soap, 5 oz. of borax, and 15 gallons of water. After fat- 
liquoring, the grains are struck out on the flesh and grain 
and dried, stored a week or two, and then dyed black. If 
the grain only is to be blacked, it is brushed with a direct 
leather black. The grain is then oiled, and the leather is 
partly dried, boarded in several directions, laid in a pile over 
night, cleaned on the grain with a little barberry juice, dried, 
and rubbed with a soft flannel rag. To obtain a bright finish, 
a glaze seasoning is applied ; and when dry, the grain is glazed, 
boarded again, given another coat of finish, dried, glazed, 
and finally boarded again. Where smooth grain is desired, 
boarding is, of course, omitted. The flesh side may be stained 
by the addition of a suitable dye to the fat-liquor, and the 
grain blacked afterwards. 

Finish for bright boarded grain leather. — Dissolve 4 oz. of 
logwood extract and 4 oz. of gelatine in 3 gallons of soft 
water. When cold, add 2 oz. of ammonia, 1 gallon of beef 
blood, 1 pint of milk, 2 oz. of ferric chloride, and 2 oz. of 
spirits of camphor. Mix 1 oz. of gelatine in milk before 
putting into the finish ; then stir together, putting in the iron 
and camphor after the other ingredients have been worked 
together. 

The dry leather should be dampened, staked, and tacked; 
and the grain should then be dampened with warm, weak log- 
wood liquor before it is finished. As soon as the grain is 
dry, apply the first coat of seasoning; dry again, and polish 
on the jack. After polishing, dampen the leather and let 
it lie awhile to allow the dampness to penetrate evenly; then 
grain from tail to foreshank and from hindshank to top of 
shoulder, and soft-board crosswise on the flesh side. Dry 
the leather, and then finish graining by boarding on the grain 
side crosswise and lengthwise. Next apply two light coats 



480 PRACTICAL TANNING 

of seasoning, the first being allowed to dry before the second 
is added. When the last coat is dry, the leather is ready for 
the last polishing. Sufficient pressure should be used to cause 
the grain to disappear and bring the brightness from the bot- 
tom of the impression of the print. After polishing, the 
leather is staked and given the last graining. Grain four 
ways on the grain side — very lightly — and the result will be 
a fine, even grain, very black and glossy. The finishing touch 
is a light coat of hot oil, made of equal parts of raw linseed, 
paraffin, and sweet oils. After being oiled, allow the leather 
to lie in a pile for a few days before it is sorted and rolled 
into bundles. Dull-boarded leather is made in the same man- 
ner, except that dull dressing is used. Printed grains are 
made by printing and graining the leather with the grain 
figure desired. 

Finishing rough leather. — Stock selected for bags and 
suitcases should be of a good light color, of soft tannage, and 
free from scratches, grubs, salt and bark stains. The best 
results are secured from sides that measure, when finished, 
about 24 sq. ft. each, and 14 lb. weight to the side should be 
the limit. The rough leather is weighed and trimmed, 25 
sides making a pack of convenient size. Wet the sides down 
over night, and stone them on the jack in the morning. Skive 
them on the belt-knife machine and split them from 2 to 4-J 
oz. per foot. The lighter leather will be the more suitable 
for suitcases and the heavier for bags. 

The next process is washing with borax preparatory to 
bleaching. If the leather is dark, dirty, and greasy, more 
borax is required than for light, clean stock. Use 25 gal- 
lons of warm water, and from 2 to 6 lb. of borax for the 
25 sides. Run the leather in this borax solution for 15 min- 
utes, then drain off the water and wash the leather in warm 
water to remove the surplus tannin and borax. The leather 
is now ready for the acid bath. Mix 1 gallon of sulphuric 
acid with 40 gallons of water and run the hides in the solu- 
tion for 10 minutes; drain the liquor out of the drum, and 
wash the leather with 3 to 4 changes of water, using 25 gal- 



FINISHING LEATHER 481 

Ions at each change. The leather should be washed until no 
trace of acid can be detected in the water coming from the 
drum. More or less acid may be used, according to the re- 
quirements of the leather. 

Next put the leather into the clean drum, with a strong, hot 
sumac liquor, and drum for a half -hour. Some tanners add 
^ pint of tin crystals and a pint of hydrochloric acid to the 
sumac liquor; others add only salt. Take the leather out, 
and place it in piles for 24 hours ; then rinse it in clear warm 
water to wash off the sumac, and strike the flesh out hard. 
If the sides are to be colored in a drum they are now in good 
condition for that process. If they are to be dried first, give 
them a coat of cod oil on the grain, and tack them on frames 
to dry. The leather should be run in the color bath for 30 
minutes, then rinsed and horsed-up. One way is to hang it 
up to dry after rinsing, without setting out as this works the 
dye into the flanks and sides. When dry, the leather may be 
dampened, set out on the grain, given a light coat of oil, and 
tacked on frames to dry. Another way consists of fat-liq- 
oring rather lightly after coloring, using fig soap and egg- 
yolk in equal proportions ; next horsing-up the leather for 24 
hours, slicking hard on flesh and lightly on the grain, then 
tacking out to dry. When dry, the leather is seasoned and 
finished. If russet leather is required, the stock, after rins- 
ing from the sumac bath, is finished without coloring. 

After the sides are dry, stake them and give the grain 
a coat of cornmeal filling. This is made by boiling slowly 
for a half-hour 1 quart of cornmeal in 1 gallon of water. 
Allow the paste to cool, then strain, and give the leather a 
good coat, rubbing it in hard. When it is struck in well, 
roll the leather and hang it up to dry. It is then ready for 
the seasoning. 

For colored and russet leathers, the following finish may 
also be recommended : Dissolve 4 oz. of blood albumen by 
standing in 1 gallon water over night; boil 4 oz. of granu- 
lated gelatine in 1 gallon of water and let it cool ; and mix | 
pint of white varnish shellac with \ pint of ammonia. Mix 



482 PRACTICAL TANNING 

these three materials together, add enough water to make 3 
gallons, and let this finish stand a week before using it. Apply 
with a sponge. For a bright finish, dry and glaze ; and for a 
dull finish, give two coats and roll while wet; then hang up 
to dry, and when dry, apply another coat. Finish by grain- 
ing, printing, or embossing. For a black finish, use any of 
the formulas given under calfskins. 

Finishing imperfect grains into patent tipping. — Among 
the stock tanned for bag and case leathers, on which a perfect 
grain is essential, after the hides are split grains are found 
which are imperfect and therefore not suitable for finishing 
with the more perfect ones. Such grains can be made into 
patent tipping, on which, the grain being buffed off, such im- 
perfections are not noticeable. The grains are taken from 
the splitting machine and washed in 50 gallons of warm water 
to which 1 or 2 lb. of borax or washing soda has been added 
for each 50 sides. The leather is washed in this water for 
30 minutes, then in cold water for 15 minutes. 

Re-tanning is done with a one-bath chrome liquor, the 
grains being run in a drum with the liquor for 2 hours, then 
piled down over night. The next morning they are washed 
in running water for 20 minutes. Three quarts of extract 
of fustic are next dissolved in a half-barrel of water, and the 
leather is drummed in the solution a half-hour, after which 
it is fat-liquored. 

Fifty sides may be fat-liquored with 2 lb. of neutral chip 
soap and 9 lb. of the best moellon degras in 50 gallons of 
water. The leather is run in this fat-liquor a half-hour, then 
piled down over night. To prepare it for finishing it is set 
out and tacked on frames to dry. When dry, it is buffed 
and staked, and is then in condition to be japanned and 
finished. 

Dressing for leather goods and furniture. — A dressing 
for goods made of leather and for leather furniture is made 
as follows: Put \ pint of hot water, -} oz. of annetto, and 
} oz. of white soap shaved fine, into a bowl, and place the 
bowl in a pan of boiling water. Into another bowl put | oz. 



FINISHING LEATHER - 483 

of beeswax, shaved fine, and put it in the pan of boiling water. 
Stir the contents of both bowls until they are melted, then 
remove them from the fire. Into the melted wax stir | pint 
of turpentine, \ pint of paraffin oil, and then the mixture of 
annetto, soap, and water. Beat the mixture until it is cold, 
then put it in a fruit jar for future use. This preparation 
may be used on brown or red leather. First wash the leather 
with hot milk, using a soft cloth or sponge. If the leather 
is faded, the dressing may be made darker by using two or 
three times the quantity of annetto. For dark green or black 
leather, a little logwood should be added to the dressing. 

Removing spots and stains from leather. — Colored 
leather, which is simply soiled or dirty and not stained, may 
be washed off with warm castile or ivory soap suds, then 
dried and rubbed. A dirty water stain is sometimes taken 
out with the juice of a lemon, which is the mildest acid that 
can be used. Vinegar also is employed for water and other 
stains. 

An oil spot may be removed by dipping a piece of rub- 
ber in naphtha and rubbing over the spot. Another way is to 
cover the spot with cement such as is used in shoe factories, 
and after the cement has dried for an hour or a little longer, 
rub or roll it off with the finger. If a little remains, go over 
it with the rubber dipped in naphtha. For dirt from the 
hands, a little oxalic acid well diluted may be used. Wash 
the dirt off and then wash with soap and water, and perhaps 
apply a little of the finish. An aniline stain cannot very well 
be taken out, but it may be helped somewhat with a rubber. 
Some of the aniline can be washed off with a regular wash, 
as with soap and water. However, the stained part of the 
leather cannot be made to look like the rest, because it has 
soaked through more or less. It depends much upon the 
leather as to how far aniline will penetrate. There are var- 
ious preparations available which shoe manufacturers use for 
stains, and some of these are employed to clean and polish 
vamps in one or more operations. Leather which becomes 
stained or discolored should be re-dyed into black stock. 



484 PRACTICAL TANNING 

Grease spots sometimes get onto the leather from oil from 
pulleys or shafting, and may be taken out with shoemaker's 
cement and chalk. Put the cement on first, then lay the 
chalk on, and work both into the leather with the flat of a 
knife or by other means. The cement will eat into the grease, 
and it should stay on until the grease comes out, even if it 
takes 24 hours or more. Use pure rubber cement for this 
purpose, as a cheap article is likely to stain the leather. The 
cement will dry after a little while so that it can be rolled off. 

Another method is to place a piece of cloth or some cotton 
waste saturated with naphtha over the spot. This is covered 
with another cloth to prevent too rapid evaporation. More 
than one application may be necessary as the grease or stain 
must dry out gradually. It is the naphtha in the cement that 
removes the grease; and it might be applied in any other form, 
provided not enough is used to bleach the leather. Slight 
spots may be rubbed out dry with a cloth saturated with 
naphtha. Ether is sometimes used. 

White ooze leather, and possibly also white grain leather, 
that has become soiled, may be cleansed with salts of sorrel 
(potassium acid oxalate, which can be procured at any drug 
store). Cold water is applied to the leather, washing it all 
over. A mixture of salt and lemon juice or salts of sorrel, 
is then rubbed over the soiled portion, with the result that all 
the spots, stains, and dirt marks disappear, and the leather 
is once more white. The leather should always be washed 
with water, which must be rubbed over the entire skin ; but 
the mixture of salt and lemon juice is applied only to the 
soiled portion. 

Bright blacking varnish for shoe leather. — This varnish 
is useful in producing a bright polish on grain shoe leather 
of any tannage. Dissolve in a bottle, tightly corked, 1 oz. 
of caoutchouc in 1 oz. of carbon bisulphide, and let the solu- 
tion stand for a few days. Next dissolve 3 oz. of orange 
shellac, | oz. of gum sandarac, 1| oz. of gum mastic, and 
5 oz. of pure Venetian turpentine in 2 quarts of alcohol. Add 
the turpentine after the other gums are dissolved. When all 



FINISHING LEATHER 485 

three materials are well mixed, add the caoutchouc solution. 
Put the vessel containing the complete mixture in another 
vessel of hot water, and heat to about 120° F. Then add 1 
oz. of spirit soluble black. Keep the whole for about an hour 
in water at 120° F. Then put it in a jar, cork tightly, and 
let it stand at least two weeks before using, as it improves 

with age. 

Two thin coats should be evenly spread on the grain with 
a sponge, and well rubbed in with a fine sponge or with a 
soft hair brush in a warm room. Let the first coat dry be- 
fore applying the second. After the last coat is absorbed, 
glaze the leather slightly by hand to produce the soft feel the 
stock had before the varnish was applied. 

A waterproof leather dressing.— Petrolatum, 4 lb. ; Bur- 
gundy pitch, 4 oz. ; rosin, 2 oz. ; ivory black (dry), 6 oz. ; and 
beeswax, 4 oz. Melt the rosin, pitch, and beeswax together, 
then add the petrolatum, and when it is melted, stir in the 
ivory black and continue stirring until the mixture is cold. 

Apply the dressing. to the leather with a soft cloth and rub 
in well. If the leather is dirty, wash it with a sponge and 
a little soap before applying the dressing. This gives a good 
black but not a polish, and if used properly, it will make 
leather soft and pliable, no matter how hard or water-soaked 
it has become. A strap treated in this way may be immersed 
in water for a week without absorbing any. Used as shoe 
dressing, it renders the wearing of rubbers unnecessary. 

A harness blacking.— Mutton suet, 2 oz. ; yellow wax, 6 
oz. ; powdered sugar, 4 oz. ; yellow soap, 2 oz. ; lampblack, 
1 oz. ; indigo, 4 oz. ; and oil of turpentine, 4 oz. Dissolve the 
soap in the water; add the other ingredients, except the tur- 
pentine ; melt and mix thoroughly together ; then add the tur- 
pentine. This mixture is applied with a sponge and polished 
with a brush. 

Blacking for vegetable-tanned leather.— The following 
is a good blacking for heavy shoe and harness leather : cop- 
peras", 9 lb. ; epsom salts, 4 oz. ; acetic acid, 6 oz. ; and nutgalls, 
1 oz. Put these ingredients into 2 gallons of soft water and 



486 PRACTICAL TANNING 

boil until dissolved; then put the solution into a barrel and 
add 40 gallons of water; stir thoroughly, and the blacking is 
ready for use. 

If the leather has a loose and open grain it is advisable to 
use 4 or 5 gallons of strong gambier liquor in place of the 
same amount of water. This will tighten up the grain and 
prevent it from piping when finished. 

Sigs for greasy leather. — To make one barrel of sig to 
clear the grain of greasy leather before applying logwood, 
use the following: salts of tartar, 12 lb.; sodium dichrom- 
ate, 5 lb.; ammonia (26°), 1 quart; and water, 40 gallons. 
Boil the tartar and dichromate in 12 gallons of water, and 
when dissolved, make up to 40 gallons, and then add the am- 
monia, stirring thoroughly. If kept for any length of time 
it may be necessary to add more ammonia. 

An excellent sig is also made as follows : Use a 50-gallon 
barrel, and boil 12 oz. of caustic soda and 12 oz. of salts of 
tartar in 12 gallons of water, and when dissolved, fill the 
barrel with cold water. 

Finishing splits: Chrome-tanned splits. — The splits taken 
off chrome-tanned hides may be finished into gusset splits or 
glove and mitten leather in much the same manner as the 
grains. First they should be leveled on the split side and 
then shaved to a uniform thickness. It is generally neces- 
sary to re-tan by drumming first in hot water and then in a 
one-bath chrome liquor for 3 or 4 hours, leaving them in the 
liquor over night. They should then be drummed for 30 
minutes, taken out, and placed in smooth piles for 48 hours. 
Washing is the next process, which is done in the same manner 
as grains are washed and neutralized ; after which the splits 
are colored. For black leather, a direct color is preferred. 
There are special black ooze dyes which are satisfactory for 
chrome splits, dyeing being effected in one operation, this 
rendering the use of logwood unnecessary. Some dyers pre- 
fer to use logwood first and top with the direct black. The 
general procedure when both dyes are employed is to use H 
lb. of logwood crystals and 4 oz. of fustic extract in 12 gal- 



FINISHING LEATHER 487 

Ions of water for 100 lb. of leather. This liquor is used at 
125° F., and the splits are drummed in it for 30 minutes. 
Then 12 oz. of direct black is dissolved in 2 gallons of boil- 
ing water, the solution is poured into the drum, and the splits 
run 15 minutes longer. Any suitable striker is next added to 
the drum, and after 10 minutes the dyeing is completed. The 
use of titanium-potassium oxalate is recommended for this 
purpose. The splits should be washed thoroughly after they 
have been dyed, pressed, and fat-liquored. If the leather is 
for mitten stock and some shade of yellow is desired, a yel- 
low dye suitable for chrome leather should be employed. Spe- 
cial glove dyes are procurable with instructions for their use. 
For mitten leather, the splits are fat-liquored once ; for gusset 
splits, twice. After applying the first fat-liquor, hang the 
splits up to dry; when dry, put them into the drum with hot 
water, and run it 40 minutes; then drain off the water and 
give the leather the second fat-liquor. Let the splits drain 
over night; then hang them up to dry. To finish the stock, 
put it in the drum with warm water, and run until soft and 
moist, or dip into hot water and place in piles over night. 
The next day tack the leather on boards, and when dry, run 
in a dry drum until soft. 

Another way to handle splits is to mill them after the 
second drying until they are soft, then stake them as smooth 
as possible and measure them. Tacking secures the greatest 
measurement and eliminates the "bag." Splits for mitten 
leather are treated in the same manner. Softness is, of 
course, the most essential quality of glove leather, and is se- 
cured by thoroughly tanning and re-tanning, and by applying 
plenty of fat-liquor. 

Gusset splits are produced not only in black but also in 
colors. There are dyes for this which can be used either 
before or after the splits have been fat-liquored and dried. 
Some dyers fat-liquor and color their leather at one opera- 
tion; but the usual practice is to dye first with basic colors 
and fat-liquor afterwards. Dyes that are not stripped from 
the leather by the fat-liquor are, of course, required. Good 



488 PRACTICAL TANNING 

penetration of the color is secured by using acid dyes in an 
ammonia bath, and after 20 minutes of drumming add formic 
acid to the drum, which ensures uniform color throughout 
the goods. 

Finish for the black. — When splits are dry after stuffing 
and setting out, pack them down in a pile for a few days; 
then whiten lightly on the back and to a fine face on the 
flesh side to be finished. Now' trim the edges and place the 
stock flesh side up on a table for the back finish. Make a 
paste for the back finish by mixing 2 lb. each of red lead 
and yellow ocher and pour in slowly and stir 1 gallon of 
cold water. Dissolve 1 lb. of corn starch in 1 gallon of cold 
water. Boil the red lead and ocher, pour in the starch, stir 
well and boil thoroughly. Let the finish cool, which is then 
ready for use. Spread an even coat on the flesh with a soft 
brush. Hang the stock up to dry and then glass with a jack. 
If the paste is too thick, add more water; and if it is not the 
color desired, change the proportions of lead and ocher to 
suit. 

Soap black. — To make a soap black, dissolve 12 lb. of com- 
mon soap in a half-barrel of water, with 2 lb. of potassium 
carbonate. Add from 12 to 15 lb. of lampblack according 
to quality. Boil slowly after the lampblack has been mixed in. 
Next add 2 pails of strong logwood liquor and 1 lb. of in- 
digo, and boil and stir thoroughly; then fill the barrel with 
cold water and add 1 pint of chloride of iron. Spread this 
black with one brush and rub it in with another. Sweep any 
smut off with a duster. If the glassing is to be done by hand, 
glass immediately after blacking. If the stock is glassed with 
a jack, hang the splits up after blacking before glassing. When 
the black is dry, they are ready to be jack-glassed. 

Flour paste. — For pasting, make a stiff flour paste by mix- 
ing 4 quarts of flour in 2 gallons of cold water. Add a little 
water at a time and stir to prevent lumps forming. When 
thoroughly mixed, boil for 10 minutes with live steam; then 
add -J lb. of tallow and | lb. of common soap, and boil until 
thoroughly cooked. Let the paste cool, and spread evenly a 



FINISHING LEATHER 489 

fairly heavy coat with a fine sponge. Hang up the splits,, and 
after the paste is dry, glass either with jack or by hand. If 
the splits will stand it, they can be oiled over the most solid 
parts on the black side. Good judgment must be used in oil- 
ing so as not to have the stock show the oil after it is finished. 

For finishing, give an even coat of gum-tragacanth dissolved 
to a thin substance. When dry, the splits are ready to be 
sorted. 

Finishing splits into Goodyears, chair splits, etc. — The splits 
are taken from the splitting machine and trimmed, then put 
into a mill with a weak tanning liquor of 6 to 8° bk., and 
milled one hour. This process breaks up the crust made by 
the belt-knife, and opens up the splits so they will take the 
re-tan liquor. When milled, they can be re-tanned in a mill 
or put back into the tan-yard for 3 weeks, using a strong 
liquor. The splits should be pulled out of the liquor every 
other day and allowed to drain for 4 to 6 hours, the liquor 
strengthened, and the splits put back one at a time. If the 
tanning is done in a mill, it will take about 6 days to make a 
good split. The splits should be milled in strong liquor about 
2 hours each day, and then left in piles the remainder of the 
day. This operation is repeated daily for 6 days, when the 
splits will be fully tanned. 

When tanned, the splits are sorted, and the heavy ones 
may be worked into flexibles or Goodyears, and the light ones 
into chair seats. 

If flexibles are to be made, the splits are put into the mill 
( after lying 48 hours after the last tanning) and given a treat- 
ment in a strong solution of epsom salts. This gives a light 
color without removing any of the tan. This solution is made 
by dissolving 75 lb. of the salts in 50 gallons of water. Use 
about 12 gallons of the solution to 8 splits. Drum them 30 
minutes, then pile them down over night. The next day set 
out and hang up to dry. When dry, dip the splits in warm 
water and lay them in piles for 24 hours; then apply a coat 
of Irish moss and soap, roll hard, and hang up to dry. When 
dry, trim and measure. 



490 PRACTICAL TANNING 

If Goodyear splits are to be made, the stock must be 
trimmed to have the proper bend for this product. The trim- 
mings are finished in the same manner as the flexibles and 
sold for cheap insoles, the bend being leveled on the splitting 
machine. Bends for Goodyears must be of uniform substance. 
After they are leveled, they are fat-liquored with soap and 
cod oil, using J lb. of soap and 3 lb. of oil to each 100 lb. 
of leather. Run them in this fat-liquor and pile them down 
over night. Then make up a clearing liquor of 2 lb. of lactic 
acid in 16 gallons of water, and run the bends in this for 10 
minutes; then dry them out, being careful to have them dry 
flat. 

When they are dry, make up a paste of 3 lb. of glue, 1 
lb. of white soap, 1 lb. of Irish moss, and 1 quart of finish- 
ing oil. Soak the glue over night in 3 gallons of water. In 
the morning add the soap, moss, and oil, and boil for an 
hour, then add enough water to make 10 gallons, and strain. 
When cold, give the splits a good heavy coat of this paste and 
hang them up until it has struck in; then roll it hard and 
treat the other side the same way. When dry, they are 
finished. 

If the light splits are to be put into chair leather, they are 
leveled on the machine, then put in a drum and given a mill- 
ing in sumac liquor, using 1 pail of sumac in 12 gallons of 
water for a dozen splits. Mill for one hour; then pile them 
down for 24 hours, and set-out on both sides and hang up to 
dry. Do not hang over sticks. Trim off all the shanks and 
thin edges. When they are dry, make up a filling paste of 
^ lb. of corn starch, ■£ lb. of dextrine, and 1 lb. of casein 
which has been soaked over night in 3 gallons of water, and 
boil this mixture slowly for an hour. While boiling, add £ 
lb. of ivory soap cut into fine shavings. This will make 10 
gallons of paste. An acid dye of any color desired can be 
added to the paste and the splits made into any color. They 
should be given a good coat of this paste, which should be 
put on smooth, and when about half-dry, the splits are rolled 
hard and dried, when they are in condition to be embossed. 



FINISHING LEATHER 491 

After embossing they are given a coat of waterproof finish 
made by cutting shellac in alcohol, and adding aniline soluble 
in spirits to the finish ; using an aniline of the same color as 
the splits, the finished goods will have a rich color. These 
splits are also often worked into cheap suitcases and bags. 

Grain leather from splits. — Imitation grain leather may be 
made according to the following instructions : The splits 
should be run through a borax bath in a drum, 5 lb. of 
borax being sufficient for 25 splits, medium size and weight. 
Heat 8 gallons of water to 75° F., and drum 20 minutes. 
Then make a bath consisting of 8 gallons with \ lb. of sul- 
phuric acid. Drum the splits in this for 15 minutes, then rinse 
in clean cold water, washing until the acid is all removed 
from the goods, then fat-liquor with 5 lb. of chip soap and 
24 lb. of neat's foot oil. Boil the soap in 3 gallons of water 
and add the oil, together with 1 oz. of sal soda. Cool to 
80° F. and run the goods 30 minutes ; then horse-up to drain. 
Next slick hard on both sides and glass on split side. Oil 
with linseed oil; then hang up or tack out to dry. 

When dry, the splits are ready to receive the color — black, 
brown, or any other color. When colored and dry they are 
ready for the moss or linseed solution. A good dressing is 
made from equal parts of glue and gelatine. Apply when 
warm, taking care not to have it too thick, and spread it on 
evenly. After the dressing has dried, the goods are em- 
bossed either in imitation of some grain or finished plain. 
This is a very necessary operation, after which the embossed 
side is given a coat of waterproof filling made of wax and 
rosin dissolved in turpentine. This is the final finish, and the 
leather is now ready for use. 

Materials used in finishing leather. — In the finishing of 
leather, materials are used that are neither oils, dyes, nor 
mordants, and are classified as finishing materials, their func- 
tion being to fill the pores and surface of the leather. They 
may be divided (1) into products of animal origin, such as 
blood and egg albumen, casein, gelatine, isinglass, etc. ; and 
(2) products of vegetable origin, such as gums (arabic, traga- 



492 PRACTICAL TANNING 

canth, and shellac), starches, dextrines, moss, etc. Some of 
the materials in common use will be briefly considered : 

Blood. — Large quantities of bullock's blood are used in fin- 
ishing leather, indeed, many seasoning liquors are nothing but 
logwood extract dissolved in warm water and then thickened 
with 5 to 10 per cent of blood. The best material to use is 
what is commonly known as de-fibrinated blood, which is 
blood that has been allowed to clot spontaneously by standing 
for several hours in a warm place, and from which the clot 
is then filtered. This de-fibrinated blood is practically a solu- 
tion of blood albumen. The clot is albuminous but consists 
of the organized or cellular structure of the blood, that is, 
the blood corpuscles. The coloring matter of the blood is in 
the red corpuscles (hemoglobin) and is carried down with 
them in the clot, while the filtered blood, if care is taken in 
its preparation, is a straw-colored fluid. To prevent putrefac- 
tion a preservative should be added to the blood as soon as it 
is filtered, carbolic acid or phenol being commonly used. 
Nitrobenzol or oil of myrbane is also used and is quite as 
effective, and although it costs a little more it is recom- 
mended as it is much less poisonous than the phenol and has 
a pleasant instead of a disagreeable odor. 

Blood albumen. — This is made from the de-fibrinated blood 
by simple evaporation in vacuum pans. The evaporation must, 
however, be conducted with extreme care so that the tempera- 
ture does not rise above 130° F., as above this the albumen 
will begin to coagulate, and when once coagulated, is valueless 
as a seasoning agent. When evaporated to a paste, the blood 
is removed from the pans and placed on screens in a warm air- 
drier. In this drier the temperature is even more important 
than in the pan, and much albumen is destroyed by overheating. 
In the United States, however, where animal by-products like 
blood albumen are controlled by large packers, these prepara- 
tions are made under scientific supervision, and there is much 
less damaged albumen on the market here than in England 
and Europe. 



FINISHING LEATHER 493 

Egg albumen. — This is prepared from the white of the egg, 
by far the largest proportion of the world's supply being manu- 
factured in China from duck eggs, and some in Russia. The 
great advantage that egg albumen has over blood albumen is 
its absolute freedom from coloring matter or iron, which 
amounts to the same thing, as the red color of blood is due 
to iron. For this reason egg albumen is used in the season- 
ing of the best qualities of glazed colored leathers. Its cost 
is always high — 5 to 8 times that of casein and 2 to 3 times 
that of blood albumen — hence it can only be used sparingly 
and on the highest-priced goods. 

Gelatine and glue. — These are both used to a considerable 
extent in finishing leather, and are also interesting to the tan- 
ner, as they are, especially the latter, by-products of the tan- 
ning industry. While there has been more or less published 
on the manufacture of these products, the industry has not 
reached a high state of scientific development. This condition 
is not the result of lack of chemical investigation, but on ac- 
count of the technical character of the subject. The present 
varieties of glue are classified as hide or skin glue, the purest 
forrn of which is gelatine, bone glue, and fish glue, and to the 
last named, isinglass stands in the same relation that gelatine 
does to hide glue. All of these varieties have a close chemical 
relation to each other, and are unquestionably complex com- 
pounds. Two principal constituents of glue have been sepa- 
rated, and are known as glutin and chondrin, the one being- 
distinguished from the other by different behavior towards 
chemical reagents. While, for example, both are precipitated 
from their aqueous solution by alcohol, only chondrin is pre- 
cipitated by acid, alum, lead acetate, etc. It also contains less 
nitrogen than gelatine and more sulphur, and, in general, bears 
a closer resemblance to albumen. The glutin imparts the ad- 
hesive property to glue, while chondrin is perhaps more essen- 
tially the jelly-forming constituent. By treatment with caus- 
tic alkalies, by a sort of hydrolysis as it were, chondrin seems 
to be converted to a considerable extent into glutin. 



494- PRACTICAL TANNING 

Chondrin is found in greater proportion in the bones, skins, 
and cartilages of young animals, and glutin in the hides of 
older animals. 

Gelatine. — As already stated, gelatine is the purest form of 
skin glue, and is prepared almost wholly from the trimmings 
of calfskins, particularly the heads and feet, which are regular 
articles of commerce for this purpose. Curiously enough, these 
have to be dried first before they will make good gelatine, 
showing that a certain degree of dehydration is necessary to 
produce the glue-forming products. The first step in the manu- 
facturing process is. the washing of the glue stock. This is 
accomplished in the ordinary cylindrical washing machine, 
not greatly different from that used in laundries. The stock 
is then limed for 10 or 12 days, with frequent changes of the 
liming liquor. After liming, a treatment with sulphurous 
acid is given to remove the lime and also bleach the stock. 
Then the stock is thoroughly washed, and given, according 
to the most approved processes, a bath of hydrogen peroxide 
to complete the bleaching and also oxidize any residual sul- 
phurous acid, the presence of even a mere trace of which is 
now forbidden by most pure food laws. Sometimes phos- 
phoric acid is used in place of the peroxide, its action being 
simply that of replacing any sulphurous acid which may be 
chemically combined with the stock. The latter is then given 
a boiling with live steam, preferably at low pressure, which 
effects the conversion into gelatine, which is then drawn off 
and allowed to gelatinize. The jelly is cut into slabs, placed 
on wire screens and dried by a dry, slightly warmed, air 
blast. When thoroughly dried, it is ground in a disintegrator 
mill and packed ready for market. 

Glue. — The preparation of glue from hides and skins does 
not differ materially from that of gelatine, except in the selec- 
tion of the stock; the treatment, however, being more rig- 
orous, and less care is necessary. When bone glue is made, 
the fat is first extracted, preferably with a volatile solvent, and 
then the bones are treated with hydrochloric acid to dissolve 



FINISHING LEATHER 495 

the phosphate of lime which constitutes their mineral matter. 
The stock thus obtained is, after washing thoroughly, boiled 
to glue in the usual manner. 

Isinglass. — This is the purest form of fish glue and is ob- 
tained from the "sounds" or air-bladders of fish. The best 
quality is made from the sounds of Russian sturgeon, which 
are air-dried, thoroughly washed, and boiled to the glue stage. 
Ordinary fish glue is made from the scales, skins, and other 
offal from fish. It is particularly adhesive glue, but its odor 
renders it objectionable for many purposes. In the prepara- 
tion of all glues, the essentials are the selection of the stock, 
and care in the manufacturing processes, particularly the avoid- 
ance of putrefaction and overheating. 

Casein, also known as "milk albumen" and "lacterine," pre- 
pared in a crude way has been used for centuries as a finish- 
ing material on various kinds of upper leather. Without ques- 
tion, much of the early Morocco and Oriental leather was fin- 
ished with a curd obtained from milk. With cow's milk, 
the separation of the curd from the whey and its utilization 
as an albuminous material was, in Scotland a hundred or more 
years ago, a considerable, if primitive industry. In the anal- 
ysis of cow's milk a distinction is made between casein and 
milk albumen, and this distinction is recognized chemically, 
although commercially, casein is frequently known as milk 
albumen. The distinction is due to the fact that milk con- 
tains two kinds of albumen, the casein or insoluble albumen, 
which separates from the whey when it becomes sour, or 
when diluted acid is added to it, and the milk albumen proper, 
which closely resembles blood albumen, but is only rendered 
insoluble by acidification and heat. 

In commerce, the casein is the only product which is util- 
ized. This is obtained as a by-product of the butter indus- 
try. The whole milk as it comes to the creamery is put 
through a centrifugal separator, in which the lighter cream 
containing the butter fats is perfectly separated from the 
heavier skim milk. When casein is to be produced, the skim 
milk must be acidified to separate it. There are three methods 



496 PRACTICAL TANNING 

of doing this : The milk may be allowed to sour spontaneously, 
in which case lactic acid is developed by the fermentation of 
the milk sugar, and this lactic acid precipitates the casein; or 
sulphuric acid or hydrochloric acid may be added to the milk. 

For many purposes the casein precipitated by the lactic acid 
is the best product, but its odor is a serious disadvantage. 
When milk ferments, not only a lactic fermentation develops 
but also putrefactive bacteria, especially of the butyric acid 
class, are present, which attack the casein itself, the result 
being, even though in slight degree, very bad-smelling com- 
pounds, so that for many purposes casein made by this process 
is almost impossible to use. 

Casein precipitated by sulphuric acid is, on the whole, prob- 
ably the best commercial product. It is troublesome to make, 
however, as the acid swells up the casein so that it is extremely 
bulky, difficult to wash, and must be squeezed in powerful 
presses to reduce its bulk and remove the excess of water be- 
fore drying. On the other hand, if hydrochloric acid is em- 
ployed as a precipitant, the casein comes down granular and 
more compact, can be readily washed, and requires no press- 
ing. The resulting casein is, however, not so satisfactory, it 
being much less soluble in the alkaline mediums, and the yield 
is low. The difference in behavior of sulphuric and hydro- 
chloric acids is interesting to the leather chemist because it 
is analogous to the action observed with these acids in connec- 
tion with the swelling of hides, wherein sulphuric acid has 
a pronounced plumping effect, while hydrochloric acid in cer- 
tain dilutions has just the opposite effect and depletes the 
hide. When the casein is precipitated and washed it is dried 
in a warm air blast, great care being taken that the tempera- 
ture does not rise much over 100° F., otherwise the casein will 
become insoluble by overheating. The casein is marketed 
either in the form of coarse scales as it comes from the drier, 
or is ground to a coarse powder, this product being often 
mixed with borax or a mixture of borax and bicarbonate of 
soda, and sold as soluble casein. Since borax is much less 
expensive than casein, it is more economical to buy the casein 



FINISHING LEATHER 497 

and dissolve it with the aid of borax, the average proportion 
used being 1 lb. of borax to 9 lb. of casein. For most pur- 
poses, equally good results may be obtained with 1 lb. of 
borax, 2 lb. of soda, and 27 lb. of casein. In the commercial 
soluble caseins, the proportion of casein is often, for obvious 
reasons, considerably reduced. If, however, a casein requires 
more borax than stated to make it dissolve, it is because it has 
been overheated in drying. 

Irish moss. — The most widely used glutinous substance of 
vegetable origin in the finishing of leather is Irish moss, some- 
times erroneously called Iceland moss. The true Iceland moss 
is a lichen which is found on exposed highlands, notably in 
Norway and Sweden, also in the Alps, and is used to a lim- 
ited extent in pharmacy. Irish moss or carrageen is found on 
all the rocky shores of northern Europe, and is particularly 
abundant on the west and northwest coasts of Ireland. In 
America, large quantities are gathered off the shores of 
Scituate, Massachusetts. 

When fresh, the plant varies in color from light yellowish- 
green to bright purple and purplish-brown, but after it is 
washed and dried in the sun it becomes lighter colored, of a 
yellowish or brownish-white shade. Viscous and fleshy when 
fresh, it dries to a semi-transparent, horny substance, the 
branching form of the plant, though somewhat shrunken, be- 
ing preserved. The preparation of Irish moss for the mar- 
ket is extremely crude, and it usually contains considerable 
quantities of sand and small shells. It is generally possible 
to purchase moss which has been prepared with more care 
and is reasonably free from these impurities at a little above 
the lowest market price, and on account of the quantities used 
this course is often the most economical. Large quantities 
are also sold in the ground form as a coarse powder, but the 
objection to this is the probability that the product is adul- 
terated with corn starch. 

'Algin. — In England, algin on a large scale is extracted from 
seaweed and sold in its purified state for purposes of leather 



498 PRACTICAL TANNING 

dressing. The method of preparation is described by Lamb 
(Leather Dressing, p. 277) as follows: 

The dried weeds are first washed thoroughly to remove as much 
inorganic matter as possible, and are then dissolved to form a thick 
jelly in a boiling solution of caustic soda. It is assumed by this treat- 
ment that an alkaline salt — sodium alginate — is produced; from this 
salt, by the addition of acid, the algin, or alginic acid, is precipitated. 
The precipitated algin is then mixed with a fresh portion of alkaline 
salt to form a more nearly neutral alginate and in this form is offered 
to the trade. 

British reports have been, as a rule, favorable to the product, 
but it never has been offered or used extensively in the United 
States until recently, when the Hercules Powder Co. under- 
took its manufacture at one of its Calif ornian plants. It is 
now also being sold in fairly large quantities by another firm 
under the trade name of "lissom." 

Algin is specially recommended for finishing skivers for 
hat leather; also for bookbinding and furniture leathers. Its 
action is much more uniform than that of the raw moss, and 
its solution keeps better, and it is more adaptable for various 
purposes. The addition of a small quantity to dye solutions 
as a thickener in table coloring is advocated as giving results 
superior to those obtained from flaxseed and gelatine which 
are usually employed. It can, however, be used only with 
acid dyes, since it precipitates the basic colors. 

Shellac. — This is obtained from gum-lac or simply lac, 
which is an exudation occurring on the small twigs or branches 
of several varieties of East Indian trees. It is produced by 
the puncture in the egg-laying operation of the female insect 
known as the coccus lacca, an insect similar to that from which 
cochineal is obtained. The gummy exudation following the 
puncture has the function of furnishing a protective covering 
for the eggs and providing food for the maggots. The female 
insect expires after laying eggs and is also enclosed by the gum. 
The best grades of lac are obtained by breaking off the twigs 
before the eggs are hatched. These twigs come into commerce 
as "stick-lac." By immersion in boiling water, the gum-lac 
is melted from the twigs, and the bodies of the dead insects; 
eggs, etc., are removed by straining. The melted lac is then 



FINISHING LEATHER - 499 

spread out into sheets by pouring it on a slowly revolving sur- 
face, the sheets broken into small pieces constituting shellac. 

Button lac. — This is obtained by simply pouring the melted 
gum on a flat surface so that it solidifies in small disks. Shel- 
lac is soluble, as is well known, in alcohol, the solution being 
known as shellac varnish. As the solubility of shellac in al- 
cohol, however, decreases rapidly with decrease in strength of 
the latter, care should be taken, if a tanner or leather finisher 
desires to "cut" his own shellac, that he use at least a full 95 
per cent alcohol ; also that he keep his alcohol and varnish 
well sealed, as high-strength alcohol rapidly dilutes by the ab- 
sorption of moisture from the atmosphere. In case the alco- 
hol has become diluted, it may be freed from water by shak- 
ing it up with fresh quicklime, and then decanting the clear 
liquid. Shellac is soluble in aqueous solutions of the alkalies, 
and also in a solution of borax, and for many purposes these 
solutions, especially that in borax, can economically replace 
the alcoholic varnishes ; that is, for those purposes where shel- 
lac is used for its adhesive or filling properties. 

Pyroxylin. — Collodion, soluble cotton, banana liquid, etc., 
are names given to the solution of nitrated cellulose in various 
solvents. Nitrated, or nitro, cellulose was first known in its 
highest state of nitration as guncotton, a high explosive, which 
is chemically a combination of the cellulose molecule with three 
nitric acid radicals. This product is obtained by immersing 
thoroughly dried and purified cotton fiber in a mixture of high- 
strength nitric and sulphuric acids. It was discovered later 
that by immersing cotton in a mixture of somewhat less con- 
centrated acids and at a higher temperature a much less explo- 
sive compound was obtained. This compound, which is com- 
posed of about equal quantities of tetra-nitrocellulose and tri- 
nitrocellulose, has the added advantage of being soluble in 
mixtures of ether and alcohol, acetone and amyl-acetate, gun- 
cotton itself being insoluble or soluble in them with difficulty. 
On evaporation of the solvent, a very elastic coating or var- 
nish is left behind, the nature of this varnish, however, de- 
pending largely upon the solvent employed. The amyl-acetate 



500 PRACTICAL TANNING 

leaves the toughest and most elastic varnish, and as such is 
largely used in the finishing of enameled and patent leathers. 
On account of its characteristic odor, the amyl-acetate solu- 
tion is frequently called banana liquid, but owing to the high 
cost of the amyl-acetate, the solutions are often diluted with 
considerable quantities of acetone. Amyl-acetate is obtained 
by the action of glacial acetic acid on amyl-alcohol in the 
presence of sulphuric acid or potassium bisulphate. 

The amyl-alcohol is the chief constituent of fusel oil, a 
by-product in the manufacture of ethyl or grain alcohol, the 
largest quantities being obtained by the fermentation of a mash 
made from potatoes. Besides the use of these cellulose solu- 
tions for patent-leather manufacture, their employment in mak- 
ing a cement for joining the laps of chrome-tanned belt leather 
is of importance to tanners. For this purpose a highly con- 
centrated solution in acetone is generally used, and the best 
cements contain also ^ to 1 per cent of red oil or castor oil, 
which seems to have the effect of making the joint less brittle. 
Indeed, it is this small quantity of oil which has been the 
secret component of many of the commercial cements, and the 
ignorance of its presence prevented belt manufacturers from 
successfully making their own cement. 



CHAPTER XVI 
WOOLSKINS AND FURS 

In the preservation of pelts where the natural hair is to 
be retained, the processes of manufacture, of course, differ 
from those already described. There are many operations, 
however, which are similar to those given in the chapter de- 
voted to leather manufacture, and as the preparation of furs is 
a branch of the leather industry, some mention of the subject 
should be made in this volume. 

Considerable skill is required in the preparation of furs, 
and in many cases extreme care must be exercised. 

Tanning woolskins: Soaking, zvashing and scouring. — 
Sheepskins that are to be tanned with the wool on, should be 
good fresh skins. Old, stale skins should be avoided, as the 
wool is likely to slip, for which there is no remedy. The skins 
should be trimmed to remove the valueless parts, then fleshed 
and washed. After washing, which is best done in a wash 
wheel supplied with running water, the pelts should be run 
through a burring machine, which removes all the burrs, twigs, 
etc. Copper sulphate is of assistance in soaking dry pelts, 
1 oz. to 15 gallons of water being sufficient, it acting as a 
germicide. Some skins merely require to be washed with 
borax and soft soap; others need thorough scouring, which 
is done to make the wool as clean and white as possible before 
the skins are tanned. It is much easier to wash the wool clean 
before than after tanning, as the -alum, salt, and other tanning 
materials set the dirt and grease, and make their removal more 
difficult. 

Scouring is done by laying the skins on a sloping table, ap- 
plying the scouring solution first to the flesh and then to the 
wool. The liquor may be made of a strong solution of soft 
soap, to which a little ammonium carbonate is added; or it 
may be a solution of soap, soda ash, and salt made in the fol- 

501 



502 PRACTICAL TANNING 

lowing manner: Add two buckets (14 quarts per bucket) of 
soft soap to 50 gallons of water in a vat or tub, then put in a 
half-pail of soda ash; turn on steam and boil the soap and 
alkali until they are dissolved; add one pail of salt and 
enough water to make 200 gallons of liquor. The salt helps 
to bleach the wool and also counteracts the caustic action of 
the soda ash. 

The scouring liquor is first well worked into the skin with 
a brush, after which it is poured into and worked thoroughly 
among the wool. The skins are next placed in waste scouring 
liquor, rinsed in warm water, and then scoured again as much 
as they seem to require. They are then rinsed in water until 
free from soap, next wrung out or drained thoroughly, after 
which they are tanned. 

Liming. — The following process of liming is satisfactory : 
A solution of 1| per cent of caustic soda is made into a thin 
paste by the addition of talc, china clay, or some similar inert 
material. This paste is applied to the flesh side, the skins 
folded up — flesh in — and allowed to stand 4 or 5 hours. They 
are then thrown into a 4 per cent solution of calcium chloride 
(4 lb. of calcium chloride in 10 gallons of water) and left 
several hours, usually over night. The pelts should then be 
washed in water in the drum and de-limed with lactic acid. 
About 4 oz. of lactic acid per dozen skins is usually sufficient. 
The skins are now ready for tanning (from the Leather 
Trades Year Book). 

Tanning. — The tanning may be done with a paste of alum, 
salt, and flour. Heat 2 gallons of water. to near boiling point, 
and stir in powdered alum until the solution is very bitter to 
the taste. Add half as much salt as alum, and allow the solu- 
tion to cool. Mix some flour with water and add the paste 
to the alum and salt liquor. This tanning paste makes the 
flesh nice and white. If yellow color is desired, add 1 lb. 
of gambier to the paste, this having been dissolved separately. 

The skins are spread on a table, flesh side up, and the paste 
is spread on evenly and liberally. The skins are then laid 
flesh-to-flesh, or folded half over the other half, and left until 



WOOLSKINS AND FURS " 503 

the next day. The paste should be applied every day for a few 
days. The skins should then be hung up to dry, and as they 
dry, worked and staked until soft and dry. One pound of 
rolled oats may be used in place of the flour, the solution of 
alum, salt, and oatmeal being boiled several minutes. The 
wet skins may also be tanned by using a mixture of powdered 
aluminum sulphate and salt — 2 parts of the former and 2 
parts of the latter — or a mixture of powdered alum and salt. 
This can be used dry, and rubbed into the flesh side of the 
skins every day for several days, when the skins will be fully 
tanned. 

Another way to tan the skins is to dissolve 8 oz. of alu- 
minum sulphate and 6 oz. of salt in a gallon of warm water, 
and apply several coats of the solution. 

A convenient way to tan the skins is to stretch them on 
frames and apply the paste or dry powder to the flesh side. 

Alum-tanned skins, before drying, should be given a solu- 
tion of soap or stearine which serves to fix the tannage so 
that it cannot be so easily removed by washing. Egg-yolk 
is also used for the same purpose. Tanning can also be done 
by immersing the skins in a solution of alum and salt, then 
drying them. Flour added to the tanning paste makes the 
skins softer and whiter. 

After the skins are dry and soft it is advisable to re-scour 
them. This should be done on a table in about the same man- 
ner as before tanning. 

Bleaching. — A permanent white can be obtained by bleach- 
ing the skins with hydrogen peroxide. The bleaching bath is 
prepared as follows : Make a 1 per cent solution of sulphuric 
acid by mixing 10 lb. of acid in 100 gallons of water. To 
this solution add 7 lb. of sodium peroxide, stirring constantly. 
The liquor is then tested with litmus paper, and peroxide or 
acid is added as required until the solution is neutral; 4 lb. 
of sodium silicate, previously dissolved, is then introduced. 
The skins are stirred in this liquor for an hour ; then taken 
out, passed through a weak solution of sulphuric acid, washed, 
drained, re-tanned if necessary, de-greased, and dried. When 



504 PRACTICAL TANNING 

dry, they are softened and run on an emery wheel to clean the 
flesh. Re-tanning is done by applying a solution of alum and 
salt to the flesh sides. 

Bleaching may also be done with potassium permanganate 
and sulphurous acid. The skins are washed and placed in a 
solution of permanganate made by dissolving 18 oz. in 120 
gallons of water warmed to 95° F. The skins are stirred in 
this solution until the wool is a good, rich brown. They are 
then removed and drained, and next placed in a bath of so- 
dium bisulphite made of 120 gallons of warm water, 7.3 
quarts of liquid 33 per cent bisulphite and 6.6 lb. of hydro- 
chloric acid. In this liquor they are. worked until they are 
sufficiently bleached. They are then rinsed, dried and finished. 

De-greasing. — Most of the grease in the skins may be re- 
moved by plastering the flesh side with a paste made of whit- 
ing and water. The skins are tacked out wet and the paste 
of whiting is applied. The skins are then placed in a warm 
room and dried. The grease is absorbed by the whiting. The 
plaster should be scraped off and another coat applied. This 
should be done until the paste dries clean and white. The flesh 
is then washed clean, and a mixture of alum and salt is ap- 
plied to replace the tanning material removed by de-greasing 
and washing. 

Some grease may be removed by brushing the skins with 
benzine, then rinsing off with hot sumac liquor. 

De-greasing may be done with benzine in the following 
manner : Make a wooden tray about 1 foot deep, 3 feet wide, 
and 4 feet long, with a rack about 1 inch thick to keep the 
skins off the bottom of the tray. Only the leather should be 
in the benzine. The lid of the tray should be made to fit in 
a slot, and be filled with water to prevent evaporation of the 
benzine. The skins are then dried and finished. 

Tanning with formaldehyde. — The skins limed, and then 
de-limed with lactic acid, may be tanned with formaldehyde. 
For each 100 parts of pelt, use 1 part of formaldehyde, that 
is, about 2\ parts of commercial formaldehyde in a convenient 
quantity of water, so that the skins can be immersed in the 



WOOLSKrNS AND FURS - 505 

solution. The skins are left in from 24 to 48 hours, then neu- 
tralized by washing in a bath containing sodium carbonate or 
borax, or a mixture of ammonium sulphate and sodium car- 
bonate; washed in clean water, drained, and fat-liquored with 
a solution of 3 parts of soft soap in 60 parts of water, then 
dried and finished. 

Tanning with a mineral and vegetable tannage. — The for- 
mula for this process of tanning is : aluminum sulphate, 5 lb. ; 
common salt, 5 lb.; gambier, 2 lb.; rye flour, 13 oz. ; and 
water, 10 gallons. 

Dissolve the sulphate and salt in a little water; also dis- 
solve the gambier by boiling in a little water. Mix the two 
solutions. The rye flour is made into a smooth paste with a 
little warm water, and the alum, salt, and gambier solution 
are added to the paste, the whole being thoroughly stirred to 
a thin paste-like mixture. This is applied to the flesh side of 
the skin with a brush, applying a coating about ^ inch thick, 
afterwards folding the skins into cushions. The goods, after 
lying some time in the wet condition, are hung up and dried. 
It is said of this method of tanning that it gives soft and 
flexible skins, and the tannage is more durable than the alum 
tannage. 

Sheep pelts can also be tanned by a chrome process by the 
methods described for furs and hair skins. 

Tanning zvith gambier. — To tan woolskins with gambier, 
first tan them with alum and salt, and then put them into weak 
gambier liquor. The dry powdered alum and salt should be 
rubbed into the wet skins, two applications being required. 
The skins are then tanned with the gambier. For 50 skins 
the addition of 1 lb. of picric acid to the gambier liquor colors 
the wool a light yellow. The liquor should be rather weak 
at the start, and strengthened until the skins are tanned 
through. Alum-tanned skins can be colored a light yellow 
by immersing them in a solution of picric acid previous to 
tanning. After they have been scoured and rinsed, put the 
skins into a bath of 15 pails of warm water, to which has 
been added 4 oz. of picric acid dissolved in a little water and 



506 PRACTICAL TANNING 

6 oz. of sulphuric acid. The skins should be moved back- 
ward and forward for 15 minutes, then rinsed in water and 
tanned with alum and salt. 

Tanning with alum, salt and hemlock extract.— Skins tanned 
by this process, and then scoured and passed through a weak 
bath of sulphuric acid, are made a golden-brown color. The 
pelts are soaked and scoured before tanning, special care be 
ing taken to get the wool clean. The tanning liquor is made 
of alum, salt and extract of hemlock bark which is weak at 
the start and strengthened as the tanning proceeds. Some 
potash soap should be added to the stronger liquor to help 
turn the wool and give the skins a velvety feel. After the 
pelts are well tanned they should be drained off and oiled on 
the flesh with a good quality of mineral oil, applied warm, 
and then hung up to dry. When dry, they are scoured with 
a strong solution of potash soap and soda ash. Both wool 
and flesh are scoured. The scouring suds are thoroughly 
rubbed into the wool and washed out again, the operation be- 
ing repeated two or three times. This scouring darkens the 
wool. A weak solution of sulphuric acid, made from \ lb. 
of acid in 10 gallons of water, is thrown onto the wool 
after it has been rinsed free from suds, and should be rubbed 
thoroughly into all parts of the wool. It changes the color 
of the wool to a light golden brown. The wool is next given 
a good blowing out with water from a hose and made as 
clean as possible, and the skins are then hung up to dry. 
Finishing consists of dampening, arm-crutching, buffing on the 
flesh side, and beating the wool soft and clean. 

Coloring. — Woolskins and shearlings may be colored any 
shade of color by the application of basic or acid dyes. Basic 
colors, however, are used chiefly on the cheaper grades of 
skins and where no particular demands are made for fast- 
ness to rubbing and washing. Where fastness is essential, 
acid dyestuffs should be used ; and in order that the skins may 
withstand the high temperature required for dyeing, they 
should be first subjected to a chrome tannage. 

When acid dyestuffs are used, the process of coloring is as 



WOOLSKINS AND FURS * 507 

follows : The skins are either tanned or re-tanned with one- 
bath chrome liquor. 'The temperature of the solution should 
be 70° F., and the whole of the flesh side should be exposed to 
the liquor. After 2 or 3 hours the skins are lifted out and 
a solution of sodium carbonate is added to the chrome liquor; 
the skins are put back and left in from 12 to 24 hours, even 
longer if thick and heavy. They are then rinsed. Any chrome 
liquor may be used, but in any case it is advantageous to add 
-|- lb. of formaldehyde to 10 gallons of liquor, which increases 
the resistance of the leather to heat. 

To increase the affinity of the wool for the dye, the skins 
are subjected to a chlorinating process. To do this, the skins 
are immersed for 15 minutes in a cold bath containing 1 lb. 
of hydrochloric acid in 10 gallons of water. Then, without 
rinsing, they are put into a bath of cold water to which is grad- 
ually added, in four portions, a clear solution of 8 to 14 oz. 
of chloride of lime for each 10 gallons of liquor. After one 
hour in this bath, the skins are re-entered into the first bath, 
in which they are worked another 15 minutes. They are 
then rinsed in lukewarm water containing 3 to 5 oz. of sodium 
thiosulphate or bisulphite in 10 gallons of liquor, to remove 
the last trace of chlorine. After pressing or hydro-extracting', 
the skins are ready for dyeing. 

Dyeing. — Black is dyed with naphthylamine black S, ESN, 
SS2B, naphthylamine blue black B, BD, naphthol black, also 
azo merino black B. Of these dyestuffs, 4 to 6 oz., calculated 
on the dry weight of the skins, are required to produce a 
deep black. Where basic colors are used, it is advantageous 
to treat the skins with acid and chloride of lime as described 
for acid dyes, then rinse and pass through a solution of tan- 
ning material — say, 2 oz. of sumac, hemlock, cutch, or que- 
bracho extract, dissolved in water — immersing for half an 
hour, then wash and color. One ounce of basic dye is gener- 
ally sufficient for two skins. To the solution of dye, | oz. 
of acetic acid and 4 oz. of Glauber's salt should be added. The 
temperature of the dye-bath should be from 100 to 110° F. 
Good, fast shades of color are also produced by immersing the 



508 PRACTICAL TANNING 

skins in a bath of sumac, hemlock, or quebracho for a half- 
hour, next immersing in a solution of titanium-potassium 
oxalate, then coloring with basic dye, 2 oz. of the tanning ex- 
tract and 1 oz. of the titanium salt being sufficient for two skins. 

To get a slight gloss on the wool, the skins should be 
passed through a weak solution of soap and oil, then dried 
and finished. Six gallons of stock soap and oil mixture are 
made by boiling 6 lb. of soap and 18 lb. of oil and making 
up to 6 gallons, ^ pint of this mixture for two skins being 
added to 10 gallons of hot water, and the skins, flesh-to-flesh, 
are passed through the bath, then dried, softened, and finished. 

In addition to the method described for dyeing woolskins 
black with acid dyestuffs, a good black can be secured by dye- 
ing with logwood, fustic, and potassium dichromate. The 
skins should be scoured and rinsed well before they are col- 
ored. The first bath consists of \ lb. of the dichromate dis- 
solved and added to 10 gallons of water at 100° F. The 
skins are doubled, flesh side in, and immersed in the solu- 
tion; then they are removed and drained. 

The second bath consists of strong logwood liquor to which 
some fustic extract and some ammonia have been added; 1^ 
lb. of logwood crystals, 4 oz. of fustic, and 1 pint of liquid 
ammonia being used for 10 gallons of liquor. The tempera- 
ture of this bath should be 120° F., and the skins should re- 
main in it until every part has been colored; they should then 
be drained and immersed in a bath of 1 lb. of dichromate in 
10 gallons of water. After the skins have been passed through 
the liquor they should be drained, and the wool should re- 
ceive an application of seal oil, well rubbed in, drained, washed, 
dried, and finished. 

Another process of dyeing woolskins black is as follows : 
For a dozen skins, a bath is prepared of 80 gallons of water, 
20 lb. of logwood extract, 3^ lb. of fustic extract, and 2 lb. 
of verdigris or copper acetate. This bath is heated to 110° 
F., and the skins allowed to remain in it for 3 or 4 hours, 
the same temperature being maintained during the process ; 
2\ quarts of acetate of iron is then added to the bath, and 



WOOLSKINS AND FURS ■' 509 

the skins left in the liquor until they are dyed black. This 
usually requires an immersion of 30 or 40 hours, during which 
time the skins are occasionally stirred. 

The skins are then drained and allowed to oxidize for at 
least 12 hours; they are then washed in warm water and 
scoured with a solution of soft soap and ammonium carbonate, 
washed and drained. They are finally re-tanned with alum 
and salt, and stretched in frames to dry. 

A good shade of tan is obtained by putting the skins, after 
washing from the tannage, into a sumac bath for a half- 
hour, 2 oz. of sumac being used for each pair of skins; next 
allow the skins to drain, and then immerse them in a bath of 
titanium salt, 1 oz. for two skins. This produces a yellowish- 
brown color. Any shade of color can be obtained on skins 
treated as described by using 1 oz. of basic dye, ^ oz. of acetic 
acid, and 4 oz. of Glauber's salt for every two skins. Colors 
produced by acid dyes are faster to rubbing and washing 
than colors obtained by using basic dyestuffs. 

Tanning furs and hair skins.— M. C. Lamb (previously 
mentioned) has described a method of tanning fur skins, which 
has advantages over the common alum tannage; the process 
is partly mineral and partly vegetable, and skins tanned with 
it are soft and durable: The process consists of applying to 
the flesh side of the skins a mixture made of alum, salt, gam- 
bier, and glycerine. The formula is: aluminum sulphate, 5 
lb.; common salt, 5 lb.; gambier, 2 lb.; rye flour, 13 oz. ; and 
water, 10 gallons. Dissolve the sulphate and salt in a small 
quantity of water, and boil the gambier until it is dissolved, 
then mix the two solutions. The rye flour is made into a 
thin paste with lukewarm water ; the oil or glycerine is added 
to the flour paste ; and finally the alum, salt, and gambier solu- 
tion is added, and the whole is thoroughly mixed to a thin 
paste-like mixture. To this, | to 1 lb. of glycerine or the 
same quantity of olive oil is added to make the skins softer. 
This addition is particularly essential when the skins are nat- 
urally of hard texture and do not possess much natural grease. 
The paste is then applied about i inch thick with a brush to 



510 PRACTICAL TANNING 

the flesh side of the skin. The skins are then folded or 
placed flesh-to-flesh, and after lying for some time, and per- 
haps receiving another application of the paste, are hung up 
to dry. 

Another excellent alum process is described in the Shoe and 
Leather Reporter: For the tanning liquor, dissolve 5 lb. of 
alum and 6 lb. of salt in 12 gallons of hot water. If the 
skins are greasy, the addition of \ lb. of borax to the liquor 
is recommended. The liquor should be warmed to 95° F., and 
the, skins occasionally moved to make the tanning uniform. 
After 24 hours the skins should be removed and coated on the 
flesn side with a paste made of alum, salt, and flour. The 
following formula makes sufficient paste for 100 lb. of skins : 
alum, 4 lb. ; salt, 3 lb. ; flour, 4 lb. ; egg-yolk, 1 lb. ; and olive 
oil, 1 lb. 

The flour is made into a paste with water; the alum and 
salt are dissolved separately in boiling water. When the so- 
lution is cool, the flour paste is stirred into it, and after the 
mixture has been thoroughly stirred, the egg-yolk and olive 
oil are added. The primary object of the flour is to obtain 
a mixture in a semi-pasty form so that it will adhere to the 
skins. If the above quantity is not sufficient to make the 
mixture sufficiently pasty, either less water should be used in 
dissolving the alum and salt, or more flour should be used in 
making the paste. The flour also helps to give fuller leather. 
The egg-yolk and olive oil give softness to the skins. For 
the finer furs, a small quantity of egg-yolk is quite essential. 
Where economy is desired, olive oil may be substituted for 
the egg-yolk, with similar results. Instead of giving a pre- 
liminary treatment in alum liquors, the tannage may consist 
of the application of the paste only. The skins should be 
allowed to lie for some time with alum paste adhering to 
them, which makes the tannage more complete and permanent. 

If it is desired to dye the furs with acid colors, it is neces- 
sary to wash them after they have been dried and worked 
soft, and re-tan them with chrome liquor. 

Soft, white, and well-tanned skins are obtained by tanning 



WOOLSKINS AND FURS " 511 

with a paste of alum, salt, and oatmeal. Heat 1 gallon of 
water and stir into it 1 lb. of pulverized alum, then add half 
as much salt as alum and boil until these are dissolved. While 
the solution is boiling, add -J lb. of rolled oats, boil 15 min- 
utes, and then set the paste aside to cool. By adding a few 
ounces of gambier to the liquor and boiling again, the skins 
treated with it will be given a light yellow color. 

The cleaned and softened skins are spread out on a table, 
flesh side up, and a heavy coat of the prepared paste is ap- 
plied with a brush. This painting is repeated every day un- 
til the skins are tanned, which takes from 2 to 6 days, ac- 
cording to their thickness. When tanned, the skins are hung 
up to dry, then stretched and worked out soft and white. The 
fur is cleaned with dry, hot sawdust, and the flesh made per- 
fectly clean and smooth by buffing on an emery wheel. 

When a large number of skins are to be cleaned a drum 
or cage is used; on a small scale they may be tramped on or 
pounded in a barrel or tub, or cleaned by brushing the hot 
sawdust into the fur with the hands, and then beating it out 
.with a supple stick. Hardwood sawdust is better than that 
from pine. 

Washing greasy skins. — Skins containing a good deal of 
natural grease should be washed in a warm solution of sal 
soda and then scraped over the beam, and the grease forced 
out of them. Dogskins should be fleshed dry, that is, before 
they are soaked, as in this condition they flesh more easily 
than after soaking. 

To wash greasy skins, prepare a warm solution of sal soda 
by dissolving the salt in water heated to 90° F. Dip the 
skins into this solution long enough to get them wet and hot, 
then put them upon the beam and go over them with a flesher 
or dull knife, bearing down hard and forcing the grease out. 
The dipping and scraping should be repeated until the skins 
are free from grease. They are then rinsed, drained and 
tanned. 

Oil process. — Furs can be tanned satisfactorily with seal 
oil. The goods are first freed from superfluous moisture by 



512 PRACTICAL TANNING 

draining or hydro-extracting, and are then rubbed over on 
the flesh with a good quality of seal oil. The skins are folded 
into cushions, flesh side innermost, and placed in a large 
wooden tub. Impregnation of the skins with the oil is facil- 
itated by a workman treading the goods with his bare feet, 
thoroughly trampling the skins down and thereby working 
the oil into them. The goods, after being worked in this way, 
are left for several hours, and then another application is 
made, and the process repeated. When the goods have be- 
come thoroughly impregnated with the oil, they are laid in a 
pile. Care must be taken that they do not reach a tempera- 
ture higher than 100 to 104° F. A tannage effected in this 
way is somewhat similar to that used in the dressing of chamois 
leather, and depends on the decomposition of the oil and the 
production of aldehydes. When thoroughly tanned, the goods 
are rinsed through a weak alkaline solution for the purpose of 
removing undecomposed oil and grease, and then are subse- 
quently dried. This is the so-called "furriers' dress process." 
To aid in this method of oil tannage the skins are sometimes 
tumbled in small drums until the heat of reaction is produced. 

Oiling alum-tanned skins. — Skins that have been tanned 
with an alum paste containing oil or egg-yolk do not require 
further oiling to make them soft, but where no oil is used in 
the tanning paste it is advisable to apply a coat of oil after 
the skins have been tanned and dressed down, or partly dried. 
Sulphonated neat's foot oil is satisfactory; so is a good min- 
eral oil. Mop the oil over the flesh of the skins, let them lie 
on a pile for a day or two, then hang up to dry. Working 
out and cleaning in sawdust completes the work. 

A solution of soap, also one of stearine, is recommended 
for alum-tanned skins. The use of either of these fixes the 
tannage and makes it more permanent. 

Deodorizing furs and rugs. — The following solution is 
useful for removing objectionable odor from furs, rugs, etc. 
Put 8 lb. of tanner's soap, or any other good bar soap, 
chipped fine, into 4 gallons of water. Add 7 lb. of sal soda. 
Boil until the soap and soda are dissolved, and while the solu- 



WOOLSKINS AND FURS 513 

tion is hot, add 1| oz. of borax and 1 oz. of oil of sassafras. 
Put the solution aside to cool, and it is then ready for use. 
This liquor can be used on skunk skins, but they should not 
be rinsed out before tanning. After the skins have been dried 
and cleaned it will be found that the bad odor has disappeared. 

Cleaning furs. — Dark furs may be cleaned with bran or 
with warm cedar, mahogany, or other hardwood sawdust. 
Beat the skin gently with a stick and brush it until it is free 
from dust, then lay it on a table with the hair side up and 
rub the hot sawdust or bran through the fur. Use plenty 
of sawdust and rub vigorously. After this, beat and brush 
the fur until it is free from sawdust or bran and is clean and 
fluffy. White furs can be cleaned in the same manner except 
that white cornmeal is used instead of sawdust. The corn- 
meal should be used warm. Soiled places may be cleaned by 
rubbing with cube magnesia. Allow the powder to remain in 
the fur for a day, then brush it out thoroughly. 

Professionals clean fur garments, muffs, etc., by dipping 
into gasoline until they are clean. They are then dried and 
the gloss is produced by passing bread crust lightly with the 
grain of the fur. 

Liming. — Where the skins are subjected to a liming - process 
before they are tanned, they work out very soft and elastic. 
In this case, however, liming is a process different from liming 
for leather. In the latter process the hair is loosened, but 
in liming fur skins and sheep pelts the hair or wool is not 
affected. The process is the same as that described under 
woolskins. 

Chrome-tanned furs and woolskins. — In order that the 
tannage of furs and woolskins may be permanent, that is, 
not affected by moisture, and the leather made as durable as 
possible, it is advisable to tan with one-bath chrome liquor. 
A commercial liquor may be used or any good one-bath chrome 
liquor employed. Where furs are to be dyed in hot dye- 
liquors, \ lb. of formaldehyde should be added to 10 gallons 
of chrome liquor to increase the resistance of the skins to 
heat. The skins are placed in this liquor and paddled for two 



514 PRACTICAL TANNING 

hours or drummed one hour. At the end of that time, 3 lb. 
of washing soda in solution is added to the liquor and the 
process is continued an hour or two longer if in the drum; or 
the skins are left in the liquor from 12 to 24 hours if in a 
paddle. They are then drained several hours, and if not to be 
dyed, they are neutralized by being washed in water contain- 
ing 2 or 3 per cent of borax, reckoned on the wet weight of 
the skins, using sufficient water to work the furs nicely. After 
this has 'been done, the skins are well washed with clean water. 

After the furs have been washed and drained, a fat-liquor 
is applied to the flesh side. Any light chrome leather fat- 
liquor may be used, and applied in the drum or brushed on the 
skins. Instead of applying the liquor in a drum, a hot solu- 
tion of sulphonated oil and flour, or of the oil alone, or a 
mixture of egg-yolk and flour, may be applied to the flesh 
side, the skins folded and left until the next day and then 
hung up to dry. An excellent method of chrome-tanning 
furs, hair skins, and sheep pelts is carried out in the follow- 
ing manner : The skins are soaked, fleshed, and washed clean ; 
they are next plumped with caustic soda and calcium chloride 
in the manner previously described, then neutralized with lac- 
tic or formic acid and tanned. 

The first step of the process consists of a solution of 2\ 
lb. of alum and 1 or 2 lb. of salt in 5 gallons of boiling water. 
When the solution has cooled to 75° F. the skins are im- 
mersed in it and stirred about for an hour, then allowed to 
remain in the solution from 12 to 24 hours. A few pounds 
of salt and 3 or 4 gallons of chrome liquor are added to each 
100 gallons of water. A smaller bath may be used by keeping 
the same proportions. As the skins absorb the tanning mate- 
rial, more concentrated chrome liquor should be added, and the 
goods are left in the solution until they are tanned through. 
When the green color has penetrated throughout the thickest 
skins, a few ounces of bicarbonate of soda should be added 
to the liquor, and the skins left in a day longer. They are 
next washed in borax water, then in clean water, drained, fat- 
liquored, and dried, or dyed immediately after the tannage 



WOOLSKINS AND FURS - 515 

is completed. A paste made of sod oil and flour forms a 
suitable fat-liquor for this tannage. 

Tanning hair skins with alum and gambier. — For the 
tanning of hair skins for rugs, robes, and mittens, a tannage 
of alum and salt, and either gambier or quebracho is satis- 
factory. The skins are soaked, fleshed, washed, and spread 
on a table and a mixture of pulverized alum and fine salt 
is rubbed into the flesh side with a brush until all spots are 
covered. Each skin is then folded down the center, or rolled 
up and left in that condition for 24 hours. A second applica- 
tion of alum and salt is again brushed in and the skins are 
left in piles a day or two longer. This treatment sets the hair 
so that it will not slip during the, subsequent treatments. The 
skins may be dried and finished without further tanning, but 
a treatment with gambier or quebracho liquor makes a more 
permanent tannage and a more durable leather. 

A fairly strong liquor is made by boiling either gambier or 
quebracho extract, and when it is cold, the skins are im- 
mersed in it and left for several days, according to their thick- 
ness. The liquor should be rather weak at first and strength- 
ened as the skins absorb the tan. 

The goods are then washed, drained, and either hung up or 
stretched in frames to dry. When the excess of moisture has 
evaporated, warm oil should be applied to the flesh and brushed 
in. Any good leather oil may be used, sulphonated oil being 
preferable. When thoroughly dry, the skins are beaten and 
brushed until the leather is soft and the hair clean. 

Cleaning white fur rugs. — These and wool rugs may be 
cleaned by the application of a paste of powdered chalk and 
water, prepared by mixing the two into a thin paste and then 
rubbing the latter thoroughly into the fur or wool and allowing 
it to dry. When dry, the paste is thoroughly brushed out 
with a stiff brush, and, to finish, a finer brush is used to remove 
every particle of chalk. This treatment takes away all dirt 
and grease and causes the goods to be clean, soft, and fluffy. 

Bleaching skins with the hair on. — Goatskins, sheepskins, 
and lambskins intended for rugs, robes, etc., can be bleached 



516 PRACTICAL TANNING 

by using a solution prepared in the following manner : 4| lb. 
of chloride of lime is added to 21 quarts of water, the 
solution being stirred for some time. It is then allowed to 
stand until it has settled, when the clear liquor is drawn off 
into a solution of 5^ lb. of Glauber's salt in 10| quarts of 
water. A precipitation results which leaves sodium hypo- 
chlorite in solution. The clear liquor, which should be quite 
free from lime, is next drawn off, and the skins are immersed 
therein until they are bleached, which takes about two days. 
They should next be rinsed in water and then washed in weak 
suds of white soap to give the necessary soft feel. Prior to 
bleaching, the skins should be washed with warm suds and 
rinsed. Alum-tanned skins may require a re-tannage after 
bleaching. This is done by rubbing powdered alum and salt, 
or a paste of the same, on the flesh side before hanging the 
skins up to dry. 

Dyeing China goatskins black. — These skins, tanned and 
made up into rugs, may be dyed black in the following man- 
ner, the quantities being for 60 rugs, which is equivalent to 
120 skins: In a vat of about 360 gallons capacity, make up 
a bath of 24 lb. of concentrated ammonia and 36 lb. of sal 
soda, previously dissolved. When these have been added to 
the water, heat to 95° F., and immerse the rugs for 2 hours, 
stirring them occasionally, then pull and let them drain 
thoroughly. 

Dissolve 50 lb. of dark turmeric, and 45 lb. of logwood 
extract, and add all to the bath. Enter the rugs and let them 
remain in the liquor until they rise to the surface. Then 
haul and add 25 lb. more of logwood extract, 10 lb. of sumac, 
10 lb. of bluestone (copper sulphate), 5 lb. of fustic extract, 
and 60 lb. of acetate of iron. Immerse the rugs for 18 hours ; 
then draw and expose them to the air for 12 hours. Heat the 
liquor again to 95° F. and put the skins back for 12 hours 
longer. Draw them out of the liquor; hang in the air for a 
time, and then wash. The washing should be done thor- 
oughly with plenty of clean running water until all dirt and 
superfluous dyestuff has been removed; the rugs should then 



WOOLSKINS AND FURS - 517 

be wrung and tacked out to dry. When almost dry, put them 
into a drum, with .a mixture of sea sand and mahogany dust, 
and run 4 hours, after which they should be put into an open 
slat wheel or cage and run for 2 hours to clean out the sand 
and dust. The latter process, if carried out properly, will be 
found to give an added brilliancy to the fur, which cannot be 
obtained in any other way. 

Dyeing furs with acid colors: Re-tannage. — The use of 
acid dyestuffs is preferable to basic colors in the dyeing of furs, 
hair skins, rugs, etc., on account of their greater fastness to 
washing and rubbing. The skins can be dyed black or fancy 
colors with acid dyes, but in order that they may stand the high 
temperature of the dye-bath without injury, it is necessary to 
re-tan them with a chrome tannage. Such a tannage not only 
increases the resistance of the furs to the hot dye-bath, but 
also makes them more waterproof and more durable. Alum- 
tanned skins in particular require such tannage. 

The skins should be placed in the chrome liquor in such a 
manner that the flesh side is fully exposed. If thrown in 
loosely, they should be stirred frequently and kept opened 
out. It is well to suspend large skins in the bath so that the 
flesh will get the full benefit of the re-tannage. 

Chlorinating the furs. — To impart greater affinity for the 
dyestuff to the skins, it is necessary to treat them with chlor- 
ide of lime in the same manner as described under woolskins. 

Dyeing.— For 100 lb. of furs, 10 to 20 lb. of Glauber's 
salt, 2 to 5 lb. of acetic acid, and the dyestuff in solution are 
added to water heated to 120° F., and the furs are placed in 
this bath. The temperature of the bath is gradually raised 
by steam to 165° F. ; and after a half-hour from 6 to 8 lb. 
of sodium bisulphate is added in 2 or 3 portions, and the skins 
worked at the same temperature for 30 minutes; they are 
then rinsed thoroughly and drained or hydro-extracted. 

After the furs have been rinsed, it is advisable to pass them 
through a solution of soap and oil, which imparts a soft feel 
to the hair. The solution is made of 1 lb. of olive oil soap, 
2 or 3 oz. of olive oil, and 1 or 2 oz. of ammonia in 10 gal- 



518 PRACTICAL TANNING 

Ions of water. The furs are worked in this solution for 15 
minutes or longer, and are then drained or hydro-extracted 
and dried without rinsing. When dry, they are worked out 
soft and cleaned. 

A rich black is obtained by dyeing the furs in the manner 
that has been described with from 4 to 6 per cent, calculated 
on the dry weight of the skins, of the following dyes : naph- 
thylamine black S, ESN, SS2B ; napthylamine blue black B, 
BD; naphthol black B, SG; and azo merino black B. As 
shading dyestuffs for black, the following are used: Indian 
yellow FF ; tropaeoline OO ; acid yellow AT ; fast yellow S ; 
and orange 11, extra. 

For blue shades : cyanole FF extra ; tetra cyanole V ; indigo 
blue N; azo wood blue SE; naphthol blue R; solid blue R; 
and formyl blue B. 

For shades of yellow and orange: fast yellow S; acid yel- 
low AT ; fast acid yellow 3 G, TL ; Indian yellow G, R ; 
naphthol yellow S; tropaeoline GO, OO; and orange GG, 
extra II, IV, R. 

For red, claret, etc. : lanaf uchsine SG ; SB ; 6 B ; azo orsei- 
ble BB; Bordeaux BL; and brilliant orseible C. 

For violet : azo wood violet, 7 R ; 4 B ; acid violet 4R S; 
and 6 B S. 

For green : naphthol green B ; fast acid green B N ; and 
cyanole green B. 

For brown: Combinations of various yellows, orange, green, 
blue, etc., are used. 

For light shades, about 0.2 to 0.5 per cent dyestuff is used, 
and for full shades up to 3 per cent dyestuff, calculated on the 
weight of the dry skins. 

For gray : silver gray N, which is dyed with the addition 
of | to 1 per cent alum without any other addition. 

Dyeing with chromate colors. — This method of dyeing 
is valuable in all cases where the demands for fastness are 
exacting. Most fancy shades can be produced with chromate 
colors, but for black it is necessary to use acid colors. 

The preparation of the skins is the same as in dyeing with 



WOOLSKINS AND FURS 519 

acid colors, except that the treatment with chloride of lime 
may be omitted, as the hair absorbs the chromate dyestuffs 
well enough without this treatment. For particularly full 
shades, however, the treatment with chloride of lime is use- 
ful also. The dyeing is carried out as follows : 

The dyestuff is dissolved in the regular manner, and half as 
much sodium dichromate as dye is dissolved in a separate ves- 
sel, and the two solutions are mixed in the dye-bath. The 
temperature of the liquor at the start should be 170° F., and 
the furs are dyed at this temperature for 1 to 2 hours. An 
addition of 1 to 3 per cent acetic acid is then made, and the 
skins are worked for another half -hour, rinsed and hydro- 
extracted. To ensure good leveling on felted wool it is ad- 
visable to use 3 or 4 per cent monopole soap. Many shades 
of yellow, brown, green, blue, red, gray, etc., are obtained by 
using the anthracene chromate dyes alone or in various com- 
binations, according to the shade desired. 

Acid and chromate colors are dissolved by pouring boil- 
ing water over them, and boiling if necessary. The solution 
should then be passed through cheese-cloth or a fine sieve, and 
any particles remaining undissolved are brought into solution 
by pouring more boiling water over them. 

Dyeing furs black with furrol dyes: Preparation of the 
skins. — Fur skins that are to be dyed are first subjected to 
the "killing" process, which cleans and de-greases the hair; 
this is done in various ways as follows : 

1. Drum killing with soda solution. — The skins are soaked 
for 3 hours in a cold solution of 1 lb. of soda ash in 10 gal- 
lons of water. They are then washed, feebly acidified with 
acetic acid, and rinsed again. 

2. Drum killing with milk of lime. — One pound of freshly 
slaked lime is mixed with 10 gallons of water. The skins 
are treated in this cold liquor, then acidified with acetic acid, 
and rinsed. 

3. Drum killing with caustic soda lye. — A liquor is pre- 
pared, according to the nature of the skin, with 6 oz. to 2\ 
lb. of caustic soda lye of 77° Tw. for 10 gallons of water, 



520 PRACTICAL TANNING 

and the skins, the flesh side of which has been spread with 
starch paste, are treated therein at ordinary temperature for 
about 3 hours. Furs with very hard hairs, such as raccoon 
skins, are left somewhat longer in the caustic soda lye. They 
are then feebly acidified with acetic acid and rinsed. 

4. Brush killing zvith caustic soda lye. — According to the 
quality of the skins, prepare a caustic soda lye solution of 
2 to 12° Tw., and brush it onto the hairs. For some special 
kinds of fur, foxskin, for instance, a stronger lye is applied 
on the belly portion and a weaker one on the back. The furs 
in this state are left lying bundled, fur-to-fur, for 3 to 8 hours, 
when they are dried, brushed, or cleaned. The skins are next 
given a drum killing as directed under 1 and 3. 

^Mordanting the furs. — The dyeing operation consists of 
two processes, namely, the mordanting and the dyeing proper. 
Mordanting of the hair is required to effect a quicker and 
fuller absorption of the coloring matter in the dye-bath, and 
is done by immersing the previously cleaned and killed skins 
in the solution of mordant, the time required depending upon 
the nature of the hair and the temperature of the bath. The 
following solutions are used as mordants : 

Quantity of Water 
Solution salt, ounces gallons 

Alum 16 10 

Copper sulphate 8 10 

Sodium dichromate 4 10 

Chrome-alum 16 10 

Iron sulphate 4 10 

These mordants are used without further additions, or else 
with the addition of 3 oz. of tartar or 2 to 3 oz. of 30 per cent 
acetic acid. The mordanting solution is best applied at a 
temperature of 68 to 77° F. For less delicate furs, the solu- 
tions may be heated to 95° F. to allow of more rapid working. 

The duration of the mordanting depends on the quality of 
the skins and the results desired; when working at a tem- 
perature of 68 to 77° F., 6 to 12 hours will be sufficient as 
a rule, and if a higher temperature is maintained the time 
may be reduced. The skins are then rinsed, and if an acid 



WOOLSKINS AND FURS - 521 

mordanting bath has been used, some soda should be added 
to the rinsing bath, the goods being once more well rinsed. 
They are then dyed. 

Dyeing black.— Black is dyed by brushing in the following: 
three ounces of furrol S and J oz. of phenylene diamine 
powder are dissolved in 1 gallon of water, and immediately 
before use, add 3 lb. of hydrogen peroxide. This solution 
is brushed on the skins three times, allowing them to dry after 
each application. 

Raccoon {imitation skunk). — These skins are brush-killed 
with caustic soda lye of 40° Tw. or drum-killed with 1 lb. 
caustic soda lye of 77° Tw. per 10 gallons water. 

The mordant solution consists of 1$ oz. of copper sulphate, 
4-1 oz. of iron sulphate, and 4 oz. of tartar in 11 gallons of 
water. 

Dyeing is done with 4^ oz. of furrol gray R and 3 oz. of 
ammonia. The black dye is brushed on in solution prepared 
as above directed. 

Lambskins. — These are drum-killed with 1 lb. of lime in 
10 gallons of water; and mordanted with 8 oz. of copper sul- 
phate in 10 gallons of water. 

Dyeing black is then done with 4| oz. of furrol S and | 
oz. of phenylene diamine powder, and 12 to 15 times the 
weight of the dyestuff of hydrogen peroxide is added to all 
the other ingredients. 

Red-haired fox.— This is dyed black by being first brush- 
killed with caustic soda lye of 2 to 3° Tw., or drum-killed 
with 12 oz. of lye of 77° Tw. in 10 gallons of water. 

The mordant solution is 1 lb. of chrome alum and 3 oz. 
of tartar per 10 gallons of water. 

The dyeing is done with 10 oz. of furrol gray R, i oz. of 
phenylene diamine powder and 20 oz. of ammonia, and hydro- 
gen peroxide, 12 to 15 times the weight of the dyestuff. 
The black dye is brushed on the skins three times, allowing 
them to dry after each application. This dyes the furs in 
imitation Alaska. 

Red-haired fox is also dyed black in the following man- 



522 PRACTICAL TANNING 

ner: The furs are brush-killed with caustic soda lye of 2 to 
3° Tw., or drum-killed with 12 oz. of caustic soda lye of 77° 
Tw. in 10 gallons of water. The mordant is 7 oz. of copper 
sulphate and 3 oz. of tartar in 10 gallons of water. 

The dyeing is done with 4|- oz. of furrol S and f oz. of 
phenylene diamine powder and hydrogen peroxide 12 to 15 
times the weight of the dyestuff, per 10 gallons of water. 

Seal rabbit {English imitation of seal). — These furs are 
drum-killed with 1 lb. of lime in 10 gallons of water. The 
mordant is 8 oz. of copper sulphate, and 3 oz. of tartar in 10 
gallons of water. 

The first dye-bath consists of 3 oz. of furrol yellow-brown 
G, 3 oz. of ammonium chloride, and -J oz. of ammonia. The 
second bath consists of 1| oz. of furrol S, 7 grains of pheny- 
lene diamine powder, 3 oz. of ammonia, and hydrogen perox- 
ide 12 to 15 times the quantity of dye, in 10 gallons of water. 

Black seal rabbit is dyed as follows : Drum-killed with 1 
lb. of lime per 10 gallons of water; mordanted with 6 oz. of 
copper sulphate and 3 oz. of tartar in 10 gallons of water; 
dyeing with 5 oz. of furrol S and 1^ oz. of phenylene dia- 
mine powder in 10 gallons of water, with hydrogen peroxide 
12 to 15 times the quantity of dyestuff. 

Tanning for robes, coats, etc. — Hides of horses and cat- 
tle that are to be tanned with the hair on them and used in 
the manufacture of coats and robes should be soaked in fresh 
water before they are tanned, in order to soften and rid them 
of dirt, blood, and other undesirable substances. They should 
be soaked long enough to become thoroughly softened, the 
length of time ranging from 12 to 24 hours. 

Dry hides are more difficult to soften than salted hides. 
Borax, salt, and formic acid are all useful in softening such 
hides. When borax is used, from 5 to 6 lb. dissolved in hot 
water, is mixed in 1000 gallons of water. The effectiveness of 
this soak is increased by raising the temperature to 90° F. 
The hides may be left in the soak for 12 hours, then worked 
on the beam or milled in a drum in a solution of borax and 
water; or they may be softened in a hide mill. After the 



WOOLSKINS AND FURS 523 

milling, they usually require further soaking to bring them 
to the proper condition. 

When a salt soak is used, enough salt is added to the water 
to make it decidedly salty. The hides may be left in the 
brine from 12 to 24 hours, next drummed in salt water for 
30 minutes, and then re-soaked until soft enough to be tanned. 

Formic acid added to the soak water hastens the softening, 
and, being antiseptic, prevents decay of the hides; a suitable 
strength is 1 or 2 lb. in 100 gallons of water. After soak- 
ing is completed, the hides should be fleshed and all flesh and 
lumps of fat removed before they are tanned. 

Alum and salt process. — In applying this process, the hides, 
after they have been fleshed, are placed in a fairly strong so- 
lution of alum and salt, care being taken to expose all parts 
of the flesh side to the liquor, so that the hair roots may be- 
come firmly set and hair-slipping avoided. The penetration 
of the liquor is hastened by warming to 85° F. before the 
hides are entered. The hides should be given plenty of room 
in the liquor so that they can be handled occasionally and their 
positions changed. It is good practice to hang them on sticks 
and suspend them in the liquor. Hides may be well struck 
through with a liquor made up of 6 lb. of alum and 12 lb. of 
salt for every 100 lb. to be tanned. They should be left in 
the tanning liquor until they become permeated with it, the 
length of time required depending upon their thickness and 
the strength of the liquor. They should then be soaked for 
a half-hour in cold water and hung up to dry. When about 
two-thirds dry they should be laid in piles for a few days to 
become uniformly soft and moist before they are dressed 
down. While the hides are in piles it is advisable to watch 
and handle them occasionally, especially in warm weather, to 
prevent heating, which causes more or less damage according 
to the degree of heat developed. 

The cutting down to a light substance is done by hand, 
work which requires considerable skill and judgment in order 
that the hide may be smooth, of even thickness, and free 
from holes. After the hides have been dressed down it is 



524 PRACTICAL TANNING 

advisable to re-tan them. They may be returned to the alum 
and salt liquor; or they may be re-tanned with alum and salt 
in a drum; and they may be re-tanned with chrome liquor. 
Re-tanning is also sometimes done with gambier or quebracho. 
One method of re-tanning is as follows : The hides are put 
in a drum with 6 lb. of aluminum sulphate and 8 lb. of salt 
in 39 gallons of water for each 100 lb. of hides. The goods 
are drummed in this for an hour. A solution of 10 lb. of 
sodium thiosulphate in 5 gallons of water is then poured into 
the mill and drumming is continued for 30 minutes, thus 
securing fixation of the tanning material on the fibers of the 
hides. The goods are then rinsed in water and hung up. 
When nearly dry, they are stuffed with oil or grease, dried 
thoroughly, then worked out soft and clean. 

By re-tannage with gambier and salt the unpleasant fea- 
tures of alum-tanned stock are prevented, and the hides are 
made soft and strong. The liquor may be applied in a drum 
or in a vat, the process being carried along until the liquor 
has thoroughly permeated the hides. They are then placed 
in piles for 48 hours, drained well, and hung up to dry. 

Softening and cleaning the stock. — For imparting softness 
to the goods, oils of various kinds may be used, also com- 
binations of tallow, soap, and oil. Mineral oils are also satis- 
factory. A heavy coat of oil should be applied to the flesh 
side, and the goods then allowed to dry slowly and kept in the 
dry condition some time before they are finished. The longer 
they are kept in the dry condition the softer they will be when 
finally finished. 

Softening and cleaning of the hides is best accomplished 
in revolving wheels or drums. The oil, grease, and dirt are 
taken up by dry sawdust in a closed drum; or in an open or 
latticed drum, the sawdust, carrying the oil and grease with it, 
is thus cleaned out of the stock. The cleaning process ought 
to be repeated two or three times to get the goods perfectly 
clean and soft. Some yellow ocher added to the sawdust 
gives the flesh side a desirable yellow color. 

Dyeing may be done with acid or furrol dyestuffs in the 
same manner as furs, which has been described. 



CHAPTER XVII 

VEGETABLE. TANNING MATERIALS 

In the manufacture of leather, advantage is taken of the 
fact that certain substances have the property of combining 
with hide substance and in so doing form a new compound 
not susceptible to decomposition. The various processes al- 
ready described plainly indicate that fact, so in this chapter 
we will consider those organic substances derived from vege- 
table matter, and which contain tannin as their active 
constituent. 

The chemistry of the tannins has not been exhaustively 
studied, so it is impossible to go deeply into the scientific side 
of the problem. Suffice it to say that the tannins are divided 
into two groups, one class being such substances as contain 
pyrogallol tannin and the other catechol tannin. 

It does not follow, however, that two substances contain- 
ing the same kind of tannin will produce the same kind of 
leather; in fact, the various tanning materials differ widely 
from each other in their chemical and physical constitution, 
but they all have the common property of precipitating gela- 
tine from solution and of combining with hide substance. Not 
only do the tannins present combine with the animal tissues 
to form leather, but the non-tannins have a decided effect 
upon the appearance and physical properties of the finished 
product. 

Those tanning materials which give a bloom to the leather 
are usually of the pyrogallol class, while those producing no 
bloom are of the catechol group. 

Many tanning materials contain certain quantities of in- 
soluble or partly soluble tannins which are known as "reds." 
These are more pronounced in acid liquors, especially sul- 
phuric, and many are completely soluble in alkaline liquors. 
These reds are taken up to a greater or less degree during 
the tanning process, and in the case of sole or heavy leather, 

S2S 



526 PRACTICAL TANNING 

have a decidedly beneficial action, causing firmness in the 
stock. 

In the production of commercial tannin solution, the bark, 
leaves, twigs, or wood form a great variety of vegetable sub- 
stances. The material is first reduced to the form of chips 
and then lixiviated with water. This lixiviation formerly was 
carried out at the tannery by leaching the bark in a series of 
tanks. As the supply of tannin material near at hand be- 
came scarce, it was found necessary to go farther away for 
it. Transportation is a considerable item, especially as the 
tannin content in most materials is comparatively small. As 
a result, manufacturers have found it more economical to leach 
the bark or wood nearer the source and to furnish the con- 
centrated extract to the tanner. Thus the manufacture of 
tanning extracts is a new industry which has sprung into ex- 
istence through force of necessity. These extracts have the 
advantage of being in a concentrated condition and are ready 
for use by simple dilution. Thus also a weak liquor can be 
quickly strengthened by adding extract, while by the old proc- 
ess it would have to be returned to the leach. 

Since the advent of concentrated extracts, the old-time 
leach-house has become a thing of the past, and although many 
tanners still leach certain barks, they all depend upon ex- 
tracts for bringing up the strength of the liquor and also use 
them to hasten the tannage. In the production of ordinary 
tanning liquor or concentrated extract the preliminary opera- 
tions are the same, and it will therefore save space to give a 
description of the two processes at the same time, carrying, 
of course, the thin liquors through the evaporation in order 
to make the commercial extract. 

Grinding. — To extract the tannin from any material it must 
first be reduced to a fine state of division, the degree of fine- 
ness depending upon the material, and may be either chips or 
powder, as found suitable. The actual method of grinding, 
as well as the machinery employed, will vary with the ma- 
terial and method of leaching chosen. 

Cone mill. — The cone mill works on the same principle as 



VEGETABLE TANNING MATERIALS 527 

the ordinary coffee mill, and is used almost exclusively for 
grinding barks. This mill (figure 115) consists of a casing, 
on the lower part of which is a toothed cone, which rotates 
within the lower part of the casing. The action may be lik- 
ened to the cutting effect of a pair of shears. The upper 
part of the casing opens up into a hopper which holds the 







Figure 115. — Eureka bark mill. 

bark. As the bark works down through the cone it becomes 
ground, the degree of fineness being regulated by adjustment 
of the cone. This machine is designed to work on dry ma- 
terial, but can be used for wet bark with no danger of 
clogging. 

Another type of mill designed for the same purpose con- 
sists of a horizontal conical runner, set with breaker knives, 
which cuts the bark into small pieces, and drops it into the 
circular casing adjoining. This also is set with knife-blades 
across which the bark is forced by the rotation of heavy 
cast-iron arms and is shaved to any degree of fineness. The 
ground bark then passes out through the base to the conveyor. 



528 PRACTICAL TANNING 

For certain materials, such as myrabolans and the like, the 
bark mill cannot be used to the best advantage. It has been 
found that these materials can be best crushed by using a 
disintegrator or some form of roller mill. The disintegrator 
is a cage-like machine having heavy arms, which travel at 
high speed in a cylinder. This machine produces an exces- 
sive amount of dust and is rather a dangerous fire hazard. 
A better type of mill for this purpose consists of two corru- 
gated rollers through which the material is passed. The dis- 
tance between the rollers determines the fineness of the 
product. 

The grinding of wood is usually accomplished in two 
stages, first by chipping the wood at an angle or directly 
across the end with machines of which two types are most 
commonly used. What is known as the "hog" is in general 
use in the United States. 

The hog chipping machine consists of a cylinder cast with 
a deep V-shaped depression on each side of which the knives, 
twelve in number, are set, through slots placed alternately and 
equidistant. Fitting the V depression is a throat or shearing 
plate bolted to the foundation frame, relative to which the 
knives must be set so they will just clear to obtain a clean 
cut instead of a smashing or splintering action. The shear- 
ing plate being adjustable, any degree of knife-set may be 
obtained. Just what this set should be is a matter of indi- 
vidual judgment and requirement. The greater the set the 
greater the capacity of the machine and also the power re- 
quired to drive it; the chip is, of course, larger and requires 
larger machines and more power to reduce it to a suitable size 
in the second stage. A fair knife-set gives not only a smaller 
chip, but one better shaped, as splintering is avoided. 

The capacity for chipping cord wood varies from 2 to 5 
cords per hour, and here we have an illustration of the im- 
portance of small things in manufacturing, for a variation 
of an eighth of an inch in the set of the knife will vary the cut 
of the machine almost the full extent of the capacities just 
mentioned, besides seriously interfering with the secondary 



VEGETABLE TANNING MATERIALS 529 

reducing machine and the ultimate yield of extract. The hog, 
for a capacity of about 4 cords per hour, or 160 cu. ft., re- 
quires about 200 h.p. to drive it. 

Disc chipper.— The other type of chipping machine is 
known as the disc chipper, and consists essentially of a heavy 
cast-iron disc, about 6 feet in diameter, mounted on a shaft. 
The knives, usually six in number, are set in slots cut 
radially or tangentially through the disc, and work against a 
shear plate on the same principle as the knives of the hog. 
The wood, however, is fed to the machine at right angles to 
the direction of rotation, and at a point about mid-distance 
between the center and outside edge of the disc, whereas 
with the hog the wood is fed against the faces of the cylin- 
der. The wood may be fed either at an angle inclining to 
the disc or horizontally, the method depending to some extent 
upon the final disposition of the spent chips. In any event 
the best results are obtained only with a forced feed, most 
suitably of the "shotgun" type, which is nothing more than 
an elongated engine cylinder with a ram on the end of the 
piston, and fitted with an automatically operated slide-valve 
to secure the quick return of the ram after the stick in proc- 
ess of being chipped has been cut up. The capacity of this 
machine is only about half that of the hog; but it requires 
much less power in proportion to the quantity of wood cut, 
and also gives a cleaner cut, with less dust, and consequently 
a chip which more readily yields its tannin. The importance 
of this will be seen later. It also reduces the work of the 
secondary machine to a minimum. 

In both types of machine the quantity and quality of chips, 
to say nothing of economy of power, are not a little depend- 
ent upon keeping the knives and shear plates sharp, so the 
knives must be changed at least every 6 hours— and oftener if 
necessary— and the shear plate as frequently as the edge be- 
comes rounded, which, considering that it is case-hardened, 
is astonishingly frequent. 

Secondary reduction.- -From the chipping machines the 
wood passes to the second stage of reduction which is neces- 



530 PRACTICAL TANNING 

sary not only to further comminute the chips, but also to ren- 
der them of uniform size before extraction. The importance 
of this will be understood if we assume that the extractors 
have a capacity and efficiency based upon chips of a given 
size. If the size is too large or the chips are irregular the ef- 
ficiency is no better than the effective extraction of the largest 
chips, and some chips are over-extracted, others scarcely wet 
through, resulting not only in loss of yield but also irregu- 
larity of product. 

The machines used for secondary reduction are of the 
swinging hammer type. The operating part of the machine 
consists of a central shaft carrying a series of plates, to which 
the beaters or hammers are loosely suspended, so that they 
hang or cluster around the center when the machine is not 
running. Upon starting the machine, the centrifugal force 
causes the hammers to assume a radial position. Just clear- 
ing the ends of these hammers a bar grating is set, conform- 
ing to the circle described by the hammers when at full speed. 
The bars cross at right angles to the direction in which the 
hammers rotate. This bar grating performs the double func- 
tion of acting as a series of shear plates and as a screen, 
which is designed to permit chips of the proper size only to 
pass to the conveyors which carry them to the extracting 
department, the size of chip being determined by the width of 
space between the bars. 

The efficiency of these machines is largely governed by the 
condition in which they are maintained. Both hammers and 
rack bars must have the shearing edge kept in condition, 
which means a rather heavy repair account, as the edges in 
neither case last more than a few days ; which is not surpris- 
ing when we realize that during a day's run of 24 hours, the 
rack bars receive the impact of the wood between them and 
the hammers over three million times. 

As good yields of extract, combined with economy, cannot 
be obtained unless the preparation of the wood is kept under 
constant control, to this end the chips should be tested at least 
three times during the 24 hours. A convenient method of 



VEGETABLE TANNING MATERIALS 531 

doing this is to screen two or three pounds of chips through 
a set of three screens superimposed in a tight box. The 
size of the openings is best at f inch, -| inch, and 12 holes 
per lineal inch; and the frame 9 by 12 inches inside 
measurement. The weighed chips are placed on the top (f 
in.) screen and shaken with a rotary motion until all that will 
pass through it. The screens are then taken out and the 
four divisions are weighed separately, and the percentage of 
each is calculated. 

A good preparation should leave no chips in the f-in. screen, 
not over 20 per cent in the \ in., and 70 per cent on the 12- 
mesh ; and there ought not to be over 10 per cent of dust in 
the bottom of the box. An excellent preparation should 
show no chips on the two upper screens, while the particles 
passing through the lower should not exceed 10 per cent at 
any time. 

Leaching. — Having been reduced to the required degree 
of fineness the material is next treated with hot water to dis- 
solve or extract the soluble portions. 

The common method of extraction, and the one that is 
simplest in operation, is the press leach. This consists of a 
number of tanks arranged in what is known as a battery, 
usually six in number. The liquor from one tank is forced 
by gravity to flow into the next in order and so on through 
the series, the same idea being carried out as described under 
the press system in making sole leather. A better concep- 
tion of the process of leaching may be secured by following 
the process through the different stages : 

Assume that the leaches have been working for some time, 
and the strongest liquor has been run off to the cooler or to 
the evaporator : This leaves six tanks full of bark, of which 
five contain liquor. The tank from which the liquor has just 
been drawn holds the least-extracted chips. Calling this tank 
No. 6, the liquor in No. 1 pit is pumped to No. 2. This 
forces the liquor from No. 2 into No. 3 and so on until No. 
6 is full. In tank No. 1 now remains the bark which has 
been extracted with six different liquors, and in so doing prac- 



532 PRACTICAL TANNING 

tically all of the tannin has been removed. The spent bark in 
No. 1 tank is now removed or "pitched" and the tank is filled 
with fresh bark. Fresh water or spent liquor is run into tank 
No. 2 which causes an overflow into tank No. 3 and so 
on through No. 6 into No. 1, which by means of proper con- 
nections now becomes No. 6. The liquor from what was at first 
No. 1 tank, but now is No. 6, is pumped to the cooler or evap- 
orator and the liquor in what was No. 2 tank, but now is No. 
1, is pumped to the next in series and the spent bark pitched. 

The tank containing the strongest liquor is called the head 
leach, while that containing the weakest liquor is known as 
the tail leach. 

The leach tanks are generally round, and are provided with 
a false bottom under which are steam pipes for the purpose 
of heating the liquor. In pressing the liquor from one leach 
to the next, the same precaution is taken as in a press-layer 
system; that is, the liquor must run downward through the 
leach in order that the incoming liquor may enter the bottom, 
thus forcing the outgoing liquor off the top. The transfer 
of the liquor is made either through wooden troughs or cop- 
per tubes by means of plugs or valves. The flow may be di- 
rected into any tank desired. 

The cooler mentioned above is a large tank or number of 
small tanks where the liquor may be held until cool enough 
for use in the yard. 

The heat during leaching should be moderate, as excessive 
heat tends to darken the liquor and produce a dark leather. 
For very light-colored stock, leaching is often carried out in 
the cold. 

Sprinkler leaches. — Some tanners and extract manufactur- 
ers use a sprinkler leach. In this system the liquor is pumped 
from the bottom of the leach, and by means of a revolving 
sprinkler is allowed to spray onto the top of the bark in the 
next in series. Although the system no doubt produces a 
strong liquor, there is danger from oxidation and consequent 
loss of tanning material. 

Autoclave system. — The systems mentioned above are all 



VEGETABLE TANNING MATERIALS 



533 



conducted at ordinary atmospheric pressure. Ap«*W 
fusion unit on the other hand consists of a serie of from 6 
to 8 cylindrical copper vessels or cells, usually of about 200 
cubic feet capacity capable of working under a pressure of 
if to 50 lb which may be operated either on the decoction 
or the continuous diffusion basis, the final results in either case 

not differing much. , 

Ea h unit or battery is piped for steam, water, and a,r 
in a manner which permits of its being operated in the same 
way aTopen leaches 'the difference being that after filling with 
wood, the cover is bolted down and the leachmg .s performed 
under a pressure of 15 to 30 pounds. , 

The time of treatment in the autoclave varies with the kind 
of wood and the degree of fineness. The time, of course^ 
much shorter than in open leaching, being reduced to a min- 
imum, from 36 to 48 hours being required to accomplish the 
complete extraction of the wood. Liquors made by the 
autoclave system contain much more sugar than those made 
tn the open leach. Just what causes the increase in sugar >s 
s"il somewhat of an open question. The liquors, as they 
come from the autoclave, go to the cooler, the clarification 
tanks or the evaporators. . 

Clarification.-Following extraction, the next step is that 
of clarifying and de-colorizing the liquors. If a simple bark 
extract is desired it is only necessary to remove the dust 
and small particles of wood carried through the false bottoms 
or strainers of the extractors. This may be and is usually 
done by precipitation in large receiving tanks, although a 
more desirable method is to filter the liquor through a rough 
filter after which it is ready for concentration. 

One important point should not be overlooked, that is the 
temperature of the liquor should be maintained as nearly as 
possible to that at which the liquor is run off. Cooling entads 
a waste of heat, and, unless pre-heat.ng is practiced the ca- 
pacity of the evaporating apparatus is much reduced. The 
temperature can, oHourse, only be maintained by rap.d han- 
dling and adequate insulation to prevent radiation. 



534. PRACTICAL TANNING 

In case of de-colorizing, and by that is meant the actual 
removal of the coloring substances by means of a coagulant, 
either chemical or organic, the process is somewhat more 
complex. Chemical reagents capable of precipitating coloring 
matter are comparatively numerous, but are not in general 
use in the United States. Most of them are defective on ac- 
count of the residual acids or bases left in the extract, which 
render them injurious to the leather. The only advantages 
they possess are that it is unnecessary to cool the liquors to 
bring about the desired precipitation, also their cheapness 

The best de-colorized extracts are unquestionably produced 
by the use of blood albumen, for which the dried packing- 
house blood of commerce is employed. The usual mode of 
procedure is to cool the liquor to about 90° F., and, while it is 
being agitated, add a strained solution of the blood in a series 
of fine sprays, the quantity depending upon the degree of de- 
colorizing desired. After the mixture is homogeneous, the 
temperature of the liquor is raised to 125° F. to ensure com- 
plete coagulation. It is then allowed to stand until clear, 
when it is drawn off for concentration. The precipitate is 
usually drawn from the bottom of the tank and passed through 
a filter-press to recover all the liquor possible. While by this 
means it is possible to produce an excellent product, possess- 
ing superior tanning qualities and suitable for tanning almost 
any kind of leather, it is somewhat expensive on account of 
the high cost of blood and the unavoidable loss of tannin. 

In addition to blood albumen, several other substances such 
as lead acetate, aluminum sulphate, barium chloride, and casein 
have been employed, all of which, however, combine to some 
extent with and cause a loss of tannic acid. 

An old method, but one which is time-consuming, consists 
in allowing the extract to stand undisturbed for several days. 
In this way the insolubles settle and the clear liquor may be 
drawn from the top. 

A method frequently used to brighten extracts consists in 
treating them with sulphurous acid. To accomplish this, sul- 
phur dioxide gas is allowed to bubble through the liquor. 



VEGETABLE TANNING MATERIALS 535 

Bleaching in this way does not actually destroy the color, but 
simply reduces it to a colorless compound which may re-ap- 
pear when the leather made from it becomes dry. 

Certain tanning materials, such as hemlock and quebracho, 
contain more or less insoluble tannin, which may be rendered 
soluble with alkalies or alkaline sulphites. Several brands of 
clarified extracts containing sodium bisulphite are therefore 
on the market. 

These extracts, as a rule, are not effective, excepting when 
applied to heavy leather in the stronger liquors of the yard. 
Applied in the tannage of light leather they are more effective, 
and a proper bleaching agent, intelligently added to the ex- 
tract, not only improves the color, but renders the tannage 
much more rapid and mellow, also giving greater tensile 
strength, pliability, and less danger from grain troubles. 

Clarification and de-colorization being completed, the next 
step toward finishing the process of making extract is that of 
concentration to a heavy syrup or powder, in which form the 
product is delivered to the tanner. 

Concentration. — From both an economic and quality stand- 
point, proper concentration is as important as any of the pre- 
vious stages, and the same principles of rapidity and low 
temperature govern success or failure in producing a high- 
grade article. 

Concentration of the extract involves the removal of the 
excess water from the light liquors, and, when it is consid- 
ered that with the open system of extraction the quantity of 
water to be evaporated is about 17, to 1 of extract, and by 
the closed system say 10 to 1, the provision for doing so must 
be quite liberal. A plant producing 10,000 gallons of 25 per 
cent tannin extract per day has to evaporate from 100,000 to 
170,000 gallons, or from 833,000 to 1,416,000 lb., of water 
daily. Should this have to be done under atmospheric pres- 
sure or open boiling it would require from 50 to 85 tons of 
coal, or its equivalent, daily. However, concentration in these 
days is accomplished altogether by boiling in vacuo or under 



536 PRACTICAL TANNING 

reduced atmospheric pressure, so that much less heat is 
necessary. 

The apparatus employed is usually known as a multiple- 
effect evaporator, of which there are several types, the most 
used being known as the standard type, which consists of 
3 or 4 copper vessels or pans, which, for the capacities previ- 
ously mentioned, would be about 9 ft. in diameter and 12 to 
14 ft. in height. These pans are arranged so that the vapor 
arising from the boiling in the first is carried to the second, and 
so on in order to the third or fourth, as the case may be. The 
lower section of each effect consists of a drum, fitted with 
two heads, which are tubed in a manner similar to a vertical 
steam boiler, but the tubes are much more numerous, a 9-ft. 
drum containing from 1000 to 1200 tubes, the number de- 
pending upon their diameter. 

Steam is admitted through the shell of the drum, and the 
heat communicated to the liquor from the outside of the tubes. 
In the center of the drum is a large tube from 18 to 24 inches 
diameter known as the well or down-take. The purpose of 
this- is to maintain a proper circulation of the liquors; any 
fluid will always move away from the hottest part or point 
of a heated surface, which, in this case, is the wall of the 
tubes. The result is that, when the liquor has become suf- 
ficiently heated to boil, it ascends the tube and is projected 
some distance above it. This gives the vapor generated in 
the tube an opportunity to escape, with the surface evapora- 
tion induced by the reduction of the atmospheric pressure. 
The liquor confined by the walls of the pan then falls through 
the down-take to the bottom to re-ascend the tube and con- 
tinue the process, the liquor gradually increasing in density 
as it passes from one pan to the next. 

The space above the drum, known as the vapor space, con- 
sists of two parts, namely, the belt and the breast or dome. 
This space is necessary for the liberation of the vapor with- 
out extrainment, which means the carrying over of any finely 
divided spray of liquor to the next drum or the condenser, 
where it would be lost with the water of condensation. Sur- 



VEGETABLE TANNING MATERIALS 537 

mounting the tubular neck of the breast is a separator, con- 
sisting of two concentric tubes with side openings diametrically 
opposite each other, the idea being to cause the stream of 
vapor to impinge upon the walls and thus cause a final sep- 
aration of vapor and liquor. 

The first effect is heated with live or exhaust steam, the 
condensation from which is usually returned to the boiler. 
The second, third, and fourth are heated with vapor from the 
preceding phase. The vapor from the last passes to the con- 
denser, usually of the spray type, and escapes with the con- 
densing water. 

Vacuum in the first two or three effects is maintained by 
a vacuum-pump, which also removes the water of condensa- 
tion. The last effect is connected by way of the condenser to 
an independent pump, which in all large apparatus operates 
on what is known as the dry system. 

After concentration, it only remains to cool and give the 
extract time for a final settling, when it may be pumped into 
tank-cars or barrels for shipment. 

In recent years some demand has sprung up for powdered 
extract, and, should this be desired, the liquid extract is dried 
by means of a film dyer, which consists of an internally steam- 
heated drum enclosed in an air-tight casing. While the drum 
revolves, it comes in contact with a trough of extract, and, 
picking up a film, carries it along the greater part of the 
revolution (during which time it is thoroughly dried) until 
it comes in contact with a scraper set against the drum, which 
removes and drops it into a suitable receiver. During the 
process the vapor is removed by a vacuum-pump. 

A recent innovation in producing solid extracts consists of 
spray drying. In this process the material to be evaporated 
is forced hot through a small opening into a high-vacuum 
chamber. The fine spray readily gives up the moisture con- 
tent, the solid material falling to the bottom of the drum. 

Powdered extract has no advantage over the liquid, except 
in saving freight charges. In fact, rather the reverse is true, 



538 



PRACTICAL TANNING 



as every exposure to heat has a deleterious effect on the prod- 
uct, both as to color and decomposition of the tannin. 

Having described the general methods employed in leaching 
or extracting vegetable tanning materials let us consider some 
of their most important sources. 

Chestnut wood. — Botanically known as the castanea vesca, 











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^ vaji' ..•■"." - '--?-.•-" 








KM •. 




£*#&&&:. 






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"""V. , •' ' * •.*"••-'■ 



Figure 116. — Chestnut trees; giants of the forest. 

it belongs to the oak family (figure 116),- and is easily dis- 
tinguishable by its narrow, pointed, serrated leaves, its fra- 
grant flower which grows in slender axillary catkins, and its 
fruit, the latter two of which are unlike those of any other 
tree. It may also be readily recognized when out of leaf by 
its bark, which, when young, is gray and smooth, but is 
heavily ridged in the mature tree. It is found from Maine 
to Alabama and Georgia* and west as far as Kentucky and 
Michigan. It does not, however, grow in great abundance 
over the entire territory mentioned, and, considered from 



VEGETABLE TANNING MATERIALS 



539 



a tanning-material standpoint, it is nearer correct to describe 
its bounds as within the environs of the Appalachian Moun- 
tains. It is one of the most beautiful of American trees, 
growing in great profusion and to considerable dimensions. 
Where it stands close, the tendency is toward height rather 
than girth and spread, and trees 80 to 100 feet in height are 




Figure 117. — A flume on the chestnut wood operations. 

not unusual. As to girth, it varies greatly, this being a mat- 
ter of age, but, as it grows rapidly, it often attains great size. 
Referring to the quick growth of the chestnut tree, it is 
so rapid that it has been termed the weed of the forest. 
Numerous cuttings in various localities show that it will grow 
as much as 6 to 8 inches diameter in 10 years, and from 15 
to 20 inches in 25 years. Besides this feature, it is repro- 
duced with great facility, a characteristic unfortunately not 
possessed by any other tannin-bearing wood of importance. 
After cutting the virgin forest it will spring up again in great 



540 



PRACTICAL TANNING 



abundance, not only as saplings but as offshoots from the de- 
caying stump left after felling the virgin tree (like the red- 
wood of California) ; and not infrequently the stems on one 
stump will aggregate more wood than the virginal trunk, so 
in 20 to 25 years a second cutting may be made. With 
proper care such a system could be continued indefinitely, 




Figure 118. — Flume terminus for chestnut wood. 



and comparatively small areas be made to yield a large supply 
of tannin for generations. 

In Virgina, West Virginia, Tennessee, and North Carolina, 
chestnut timber grows in great abundance, and large tracts of 
well-timbered land exist upon which 75 per cent or more of 
all the timber standing is chestnut. It is in these States that 
the production of chestnut tannin is mostly conducted. 

The air-dried wood, the operations of handling being shown 
in figures 117 and 118, contains an average of about 8 per 
cent of tannin, but it varies a great deal and may run as high 
as 14 per cent. The age of the tree, exposure, and climatic 



VEGETABLE TANNING MATERIALS 541 

conditions all have their effect upon not only the tannin but 
the other extractive constituents of the wood. 

Besides tannin, it contains considerable quantities of gal- 
lic acid, the pre-existence of which is doubtful, as it may 
result from the decomposition of the tannin. 

The extractive matter obtained in the manufacture of chest- 
nut tannin extract usually contains about 60 to 65 per cent 
tannin and 35 per cent to 40 per cent non-tannin substance. 
The tannin is distinctly of the pyrogallol group, yielding pyro- 
gallol when heated, and remaining soluble when tested with 
bromine water and hydrochloric acid- formalin solution. When 
pure, it also gives the blue-black color said to be characteristic. 

The non-tannin substances consist chiefly of sugars, which 
reduce Fehling's solution, gallic acid, pectose compounds, resin 
and ash, but they are no better understood than the tannins. 
Their quantity and composition in the tanning extract are 
largely a question of manufacture, and much remains to be 
done before we can say much about them. The sugars of 
chestnut wood, in common with those of barks, are valuable 
in the tannery on account of the acid they produce ; thus their 
presence adds to the value of chestnut tannins. 

As a tanning material, chestnut tannin has been chiefly con- 
fined to the production of sole, belting, and other heavy leath- 
ers; but there is no reason why it cannot be employed for 
many other classes of leather when properly made and used. 
On account of its abundance, cheapness, and excellent quali- 
ties, chestnut tannin bids fair eventually to become the staple 
basis for the tannage of all heavy vegetable-tanned leather. 

A few years ago the chestnut blight struck the trees along 
the North Atlantic coast, and before steps could be taken to 
retard its ravages, thousands of trees were destroyed. It is 
felt, however, that proper treatment has been discovered and 
that the danger is now past. 

Oak wood. — The wood of all the oaks yields considerable 
though varying quantities of tannin, the American oaks rang- 
ing from 3 to 5 per cent in the air-dried woods. In Europe, 
tanning extracts are made from a number of the oak woods, 



542 PRACTICAL TANNING 

the product being held in much favor, if one may judge from 
its value, which is from 20 to 25 per cent higher than the 
chestnut extracts. 

Among the oaks employed for this purpose are the Q. 
robur, Q. cerris, Q. pubescens and their varieties. These 
grow chiefly in southeastern Europe, Austria, Hungary, and 
Jugo-Slavia being the chief sources of supply. In America, 
no oak-wood extract is produced. Attempts were made years 
ago to utilize the wood of the chestnut oak or rock oak, O. 
prinits, the wood and bark being all ground up together. The 
composition of the extract, however, did not, apparently, meet 
the ideas of the American tanner at that time, so the attempt 
failed, and no further investigation has been made up to this 
time. 

In Europe, only the waste material from the sawmills is 
utilized for extract, the body of the tree being more valuable 
as lumber; and, in order to produce a merchantable article, 
the bark, which contains red coloring matter, is carefully dis- 
carded. The tannin of the oak woods is similar in most re- 
spects to that of chestnut. It belongs to the pyrogallol group 
and gives the same reactions. 

Extract made from oak wood appears to differ little in 
composition and color from American chestnut, but it usu- 
ally contains more soluble non-tannin than the average Euro- 
pean chestnut. A recent analysis of a sample of southeastern 
Europe oak-wood extract gave approximately 38.6 per cent 
total solids, ^25.0 per cent tannin, and 13.2 per cent soluble 
non-tannin. The purity was 65 per cent, or almost identical 
with American chestnut. 

Barks.- — Tanning in all countries, until recent times, was 
conducted with native materials derived from the most con- 
venient sources of supply, and as in Europe and North 
America, the immense forest areas, now sadly depleted, fur- 
nished what was at one time considered an inexhaustible sup- 
ply of oak and hemlock bark, it naturally followed that the 
tannins derived from these barks formed the basis of all tan- 
nages on both continents for a very extended period. 



VEGETABLE TANNING MATERIALS 543 

In Europe and Great Britain the oak barks predominated, 
while in North America hemlock bark has been more exten- 
sively used, although oak bark has been, and is used where 
plentiful, especially in the Southern States. 

Speaking of the oak barks, it seems that the source of sup- 
ply of tannin is not confined to any one species, and almost 
any oak bark that would tan has been employed. There are 
altogether over 30 species and varieties of oak trees. 

Abroad, the Q. robur, or English oak, has been most exten- 
sively used. This tree bears a greater resemblance to the 
American white oak than any other, though it is interesting 
to note that the bark of the latter is scarcely recognized here 
as a tanning material. This tree, which is more valuable now 
for its timber than for its bark, grows throughout Great 
Britain and Europe and still furnishes, through reforestation, 
a considerable quantity of tan bark. In Europe, the custom 
is to peel the bark from the tree while it is still young enough 
to be smooth, the age of the tree being from 12 to 20 years. 
The bark, it is claimed, then has a greater tanning efficiency 
and yields a better color than that from mature timber. 

Many plantations have been started during the past 50 or 
60 years, which are said to have yielded profitably. In 
handling these plantations,, the system is to divide them into 
as many sections, as it takes years to produce bark suitable for 
peeling. When the bark has grown sufficiently, the first sec- 
tion is peeled, the timber removed, and the land re-planted or 
allowed to sprout from the stump of the first growth. The 
next year the second section is harvested, and so on in rota- 
tion, so that a continuous supply is secured. Europe is much 
in advance of the United States in the line of conservation, 
the necessity for such expensive development not yet having 
arisen on the American continent. In fact, it is doubtful if 
such a system could be successfully applied here, as it is 
obvious that the labor and attention must be costly, and, as 
long as tanning material is as cheap as it is now, it is not 
likely to appeal to the investor. 

The American varieties of oak are more numerous than 



54>4> PRACTICAL TANNING 

those of Europe, there being about twenty-eight, but the chest- 
nut oak or rock oak, (Q. prinus) is the only one which fur- 
nishes tanning material in great quantity. The range of this 
tree may be said to be confined, like the chestnut, to the Appa- 
lachians, where it grows in great abundance; although the 
supply is diminishing rapidly, and will soon be exhausted, as 
it does not reproduce as rapidly as chestnut. In appearance 
it is very similar to some of the other oaks, but, while in 
foliage, may be readily distinguished by its leaf, which is 
unlike any of the others. In appearance it is something be- 
tween the chestnut and the English oak. In Winter, the 
expert may distinguish it by its bark, which is smooth and of 
a silvery gray color in the young tree, and rough and much 
ridged in the mature tree. The bark becomes rough after 
the tree has attained a diameter of 8 inches or so. 

In the United States, bark is peeled from trees at all ages, 
and consequently the quality and tannin content vary a great 
deal. 

In past years the tree was felled for its bark alone, the 
timber being considered of little value. Now, however, little 
is cut that is not manufactured into lumber, a Change which 
has made for conservation, the peel being governed to a con- 
siderable extent by the market for the timber. 

Prime chestnut-oak bark contains an average of about 10 
per cent of tannin, and yields 18 to 20 per cent of soluble 
extractive matter, which is rich in acid-forming sugars. It 
is on this account considered one of the most valuable of all 
tanning materials. It has now become too scarce and costly 
to use alone, but when it was available it was unsurpassed 
for the manufacture of sole and belting leathers. In com- 
bination with other materials, it yields a high class of car- 
riage, harness, and other leathers requiring a full, mellow, 
and firm tannage. 

The tannin of the chestnut oak responds to the catechol 
reactions, and is unlike some of the other oaks in this respect, 
as several seem to contain tannins of both groups in large 
proportions. 



VEGETABLE TANNING MATERIALS 545 

On the Pacific Coast there is another variety of oak tree 
which is deserving of more study than has been given to it, 
and which bears the same relation to the tanning industry 
of that region that the chestnut oak does to the East: It is 
the Q. densiflors or California oak. It is still abundant in 
California and Oregon, growing chiefly on the lateral spurs 
of the Pacific coast ranges, which makes it somewhat inaccessi- 
ble. The bark from this tree is the richest of all the known 
oaks in tannin, frequently containing from 17 to 20 per cent, 
with as much as 30 per cent of soluble extractive matter. It 
yields a rich red liquor, more like that of hemlock in appear- 
ance than of chestnut oak. The sole and harness leather tanned 
with it is of a distinctive character and of excellent quality, 
being much more mellow and with less tendency to break than 
ordinary oak-tanned stock. 

It seems to differ from most other tannin in that it is 
difficult to blend with other materials on account of an ap- 
parent selective action. In other words, when blended with 
chestnut liquors, the hide seems to take up the chestnut first, 
with the result that, not only is the characteristic color lost, 
but the texture of the leather is materially affected. 

Chestnut bark. — In the manufacture of chestnut-wood ex- 
tract, no attempt is made as a rule to separate the bark from 
the wood proper, both being extracted at the same time. 
There is, however, a certain demand for chestnut-oak bark 
extract and when this is required it is extracted separately. 

Oak bark. — Nearly all species of oak contain more or less 
tannic acid in the bark and wood. Catechol tannins predomi- 
nate in the bark, although this also contains a certain amount 
of pyrogallol tannins, ellagitannic, and quercetannic acids. 

If cut while the sap is rising, the bark separates readily, 
while timber cut at other times offers some resistance in strip- 
ping. The peeled bark is laid in piles several feet high and 
is so arranged that the water is shed somewhat as from shingles 
on a house. This is absolutely necessary to prevent damage 
to the bark. When oak bark is used it is generally leached at 
the tannery. No true oak-bark extract is on the market, al- 



546 PRACTICAL TANNING 

though a so-called extract is sometimes offered for sale. Such 
extract is usually found to be modified chestnut-oak bark. 
In some of the Southern tanneries and extract works a cer- 
tain amount of oak-wood extract is prepared; but the quantity 
is comparatively small. 

Hemlock bark. — After the oak tanning woods and barks, 
the bark of the hemlock tree, tsuga canadensis, ranks next in 
importance and, in North America, it probably still occupies 
the premier position. 

The hemlock is a cone bearer of the spruce family, and is 
one of the most beautiful evergreens of the forest. Con- 
ical in shape, with plume-like horizontal branches, it gives an 
impression of great dignity, and, in the forest, of much sol- 
emn beauty. The bark is of a red color, and its leaves are 
short and linear, growing on little petioles, Which distinguish 
it from any other conifer. In Spring the foliage is tipped 
with new growth of a light green, while in Winter it is dark 
and lustrous. 

It is widely scattered in one or more of its varieties all 
round the world. The species are five or six in number, and 
grow principally in northern latitudes. In eastern North 
America it ranges from Hudson Bay to northern Georgia, 
and from the East to the Mississippi. The great hemlock for- 
est, however, does not extend south of Pennsylvania and West 
Virginia, the timber south of those States being only found 
in restricted areas, mostly following in narrow belts the small 
water-courses of the mountains. 

In western North America another variety of this tree, the 
tsugas mertensiana, which is richer in tannin than the eastern, 
flourishes along the Cascade Range and north from there along 
the mountain ranges of British Columbia and Alaska, where 
it is still very abundant on account of the remoteness of its 
position, half a continent separating it from the great centers 
of the leather industry. 

In the Eastern States the supply is fast approaching the 
vanishing point and of the thousands of square miles once 
covered with practically unbroken hemlock forest, compara- 



VEGETABLE TANNING MATERIALS 547 

tively little remains, and it would doubtless have entirely dis- 
appeared but for the introduction of other tanning materials, 
and the increased value of the timber. 

In Canada there are still considerable areas, which, however, 
are so rapidly disappearing that it is only a matter of a short 
time until the hemlock forest disappears from the eastern sec- 
tion of the continent. 

In northern Europe two species of this tree are found in 
quantity, and also in Asia, while other varieties grow in India, 
China, and Japan. From descriptions given by various au- 
thorities it would appear that the Oriental hemlock is very 
similar to the American. 

The bark of the hemlock contains varying quantities of 
tannin, this being governed by climate and exposure. As a 
rule it will yield about 10 per cent of the weight of the air- 
dried bark, with about 16 to 18 per cent of soluble extractives. 
The tannins are of the catechol group, and the soluble non- 
tannins are rich in sugar. The liquors are of a brilliant red 
color and are soluble with difficulty, and like most of the 
catechol tannin bearers, are not readily filtered clear. 

As far as North America is concerned, it has been the 
tanning material par excellence, and probably the only one 
with which it is possible to produce excellent leather of all 
kinds. It seems as well adapted for the lightest colored 
fancy or upper leather as for the heaviest sole, and, previous 
to its scarcity, it was used almost universally in the whole 
range of leathers made on this side of the Atlantic. 

Quebracho. — From the standpoint of production and con- 
sumption, quebracho wood tannin is as important as chestnut 
wood. 

The quebracho tree is generally given in botanical books 
as aspidospermia, but this name covers several varieties, which, 
with one or two exceptions, are of little or no use to the 
tanner. The variety with which he is chiefly concerned is 
that growing in Argentina and Paraguay, and known as the 
quebracho Colorado or, as distinguished by botanists, the 
loxopterygium lorentzii. The common trade name quebracho 



548 



PRACTICAL TANNING 



is said to be derived from the Spanish word quebra — to break, 
and hacho — axe, or break-axe, this nomenclature doubtless 
being due to the great hardness of the wood. 

The quebracho is an evergreen tree, which, in common with 
all others, is of all heights and sizes. It is said, however, 
occasionally to attain a height of 100 feet. In the forest its 
distinguishing features are its usually erect stem and its wide- 




Figure 119. — Carting quebracho logs to port of shipment; trees in 

the background. 

spreading crown. The branches at the top grow almost ver- 
tical, but, as they descend, become gradually more horizontal 
until they droop, forming a somewhat umbrella-like top. 

The leaves are rigid and lanceolate or spearhead-like in 
shape, and the flowers occur in terminal panicles. 

The bark is thick, and remarkable for the thickness of the 
internal or corky layer, which often constitutes one-half of 
the entire thickness. 

The wood is very heavy, too heavy to float, and of a red- 
dish-brown color,, which takes a fine polish. 

This tree (figure 119) is of extremely slow growth, taking 



VEGETABLE TANNING MATERIALS 549 

from 400 to 600 years to attain a girth of 6 to 8 feet, a 
characteristic which makes its disappearance only a matter of 
time for it certainly is being cut much faster than it grows. 
The supply, as far as at present ascertained, is confined to 
Argentina and Paraguay, the Chilean supply, it is said, hav- 
ing already been exhausted. There are, however, large quan- 
tities still standing on the grand chaco or forest section of 
the two countries first named. 

Unlike the hemlock, oak or chestnut forests of America, 
where immense bodies of these timbers grow almost to the 
exclusion of any other, the quebracho grows scattered through- 
out and mingled with the other growths, nor is the forest like 
that of our mountainous country. The land on which it 
grows is for the most part flat or rolling, and the forest is 
divided into belts, a bek of timber alternating with a cleared 
space of pampa or prairie. ■ 

It was estimated some years ago that there were 175 mil- 
lion tons of timber standing, but, as this estimate was apparent- 
ly based on the chaco being an unbroken forest, its accuracy 

is open to question. # 

The manufacture of quebracho tannin is conducted for the 
most part in Argentina, a number of factories operating on 
the Parana river and its tributaries, to which the logs are 
conveyed, in some instances, hundreds of miles, by rail and 
boat These logs are also transported to Germany and the 
United States where the tannin extract is produced in large 

^Quebracho has been used for tanning in Chile and Argen- 
tina for a long time, but it is only within the la* 20 years 
that Europe and the United States have utilized it to any 
creat extent. In the latter country its use grew tremendously 
for some years, more being consumed here than m all of 
Europe At present the annual consumption of the States is 
about 90 million pounds of solid extract per annum, represent- 
ing about 56 million pounds of tannin, or the product from 
156 000 tons of wood. The quantity used in Europe is prob- 
ably not quite so great. Germany is the largest consumer on 



550 PRACTICAL TANNING 

the Continent, and, although some is used in France and Great 
Britain, it is not looked upon as favorably as in America. 

The wood contains about 18 per cent of tannin and yields 
22 to 25 per cent of extractive matter, of which 80 per cent 
is estimated as tannin and 20 per cent non-tannin. The tannin 
belongs to the catechol group, giving a green color with ferric 
alum, and precipitates with bromine water and hydrochloric 
acid-formaldehyde solution. This, however, only applies to 
crude and some clarified extracts. It has been found that some 
of the so-called clarified do not yield precipitates with either 
of the above reagents, which is due to the presence of the 
chemicals used for rendering the extract soluble, or clarify- 
ing it, as it is usually termed. 

The non-tannins differ materially in their structure and 
proportions from those of oak and hemlock barks and chest- 
nut wood. Some tests show that an extract containing 10 per 
cent non-tannin contains about 2 per cent gallic acid and 1.25 
per cent sugars : the remaining 6.75 per cent is probably gum 
and pectose matter, although that still remains undetermined. 

The extracts, which are of a strong red-brown color, are 
soluble with great difficulty in water, and, in order to obtain 
anything like economical or satisfactory results, it is neces- 
sary to resort to some one of the several methods of clarify- 
ing them either by sedimentation or chemically rendering them 
soluble, the most common method being to treat the extract 
with sodium bisulphite. 

As a tanning agent, quebracho is employed for all classes 
of leather, being especially adapted when clarified for the 
tannage of light leathers where weight and plumpness are 
not a consideration. In conjunction with hemlock and oak 
bark or their extracts, it is extensively used in the produc- 
tion of bag, case, patent, and automobile leathers ; and many 
satisfactory tannages are produced in the above lines where 
it forms almost the entire tannage. For heavy leathers, such 
as sole, belting, and harness, it is invariably used in conjunc- 
tion with other materials, as it does not contain the necessary 
sugars for acid- forming, which in these tannages is indispensa- 



VEGETABLE TANNING MATERIALS 551 

ble; nor does it make solid leather of good weight when used 
alone. When clarified, however, it penetrates rapidly, and on 
account of its high purity, is useful in strengthening up a 
yard which has become saturated with inert non-tannins. 

Valonia. — This tanning material is obtained from the acorn 
cup of the Turkish oak (quercus cegilops), which grows in 
Asia Minor, and, being shipped from Smyrna, is termed 
"Smyrna valonia." The amount of tannin in this grade of 
valonia is about 40 per cent. A lower grade of valonia grows 
on the islands of the Grecian Archipelago and is known as 
"Greek valonia." The tannin content of Greek valonia ranges 
from 20 to 30 per cent. In both varieties the tannin is mostly 
of pyrogallol derivation. 

Valonia is of value to the tanner for its weight-giving qual- 
ities. It also deposits considerable bloom, not only in the 
leather, but on the surface. In most tanneries valonia is used 
as a dusting material in the layers. The tannic acid from 
valonia is found both in the cup and in the beard hair. As a 
rule, however, no attempt is made to separate the two mate- 
rials. In a few places where they are separated the ground 
cup is used for dusting and the beard hairs are extracted. The 
extract from the beard hairs produces a certain quantity of 
acid in the yard, while the cup gives practically no free acid. 

In the use of valonia it has been shown conclusively that 
Smyrna valonia gives about 25 per cent more weight than 
Greek valonia, hence the former is much more prized by 
tanners. 

In Asia Minor the fruit ripens during July and August, 
and the acorns, which are shaken from the trees, are allowed 
to dry on the ground. They are then gathered and trans- 
ported by camel and rail to Smyrna, where they are placed 
in storage and allowed to ferment, during which time the 
acorn contracts and falls from the cup. The cups are hand- 
picked, the largest and finest, known as prima, going to Trieste, 
the second selection (Inglese) is shipped mostly to England, 
while the remainder, known as natural, is sent to other 
countries. 



552 PRACTICAL TANNING 

In Greece, the best fruit is gathered in April, while still 
green, and is known as chamada. The second quality is beaten 
from the trees in September and is known as rhabdisto, while 
a third grade is collected after the fall rains, and being dark 
in color, is termed charcola. 

Mangrove bark. — This tanning material is derived from 
the bark of the mangrove tree, which occurs widely distributed 
in practically all tropical island districts. There are over 
20 different species of mangrove, all of which contain more 
or less tannic acid ranging from 8 to 30 per cent. The most 
largely used species of mangrove is that known as rhisophora 
mucronata, although bruguiera gymnorrihiza and ceriops con- 
dolleana are somewhat employed. The mangrove tree re- 
quires considerable moisture and is therefore found in swampy 
or marshy land, also along muddy sea-coasts. The trunk is 
irregular and spready, making gathering difficult. The bark is 
stripped and sold as such to the tanner, or is extracted and 
sold as mangrove or cutch extract. Mangrove is used by 
many tanners of sole leather, mixed with other barks and ex- 
tracts. In some South American countries the entire tannage 
consists of this material. No doubt the difficulty of securing 
the bark has been the cause for its retarded utilization. There 
are thousands of acres, however, of this valuable tanning 
material available, and there is no question but that eventually 
it will become an important raw material in the manufacture 
of leather. 

Gall nuts. — Quercus infectoria is the source of Turkish 
galls. The galls are caused by insects which lay their eggs 
on the leaf or bud and so produce an abnormal growth. The 
best gall is obtained before the insect escapes, and contains 
from 50 to 60 per cent of tannin as gallotannic acid. This 
material is the principal source of pure tannic acid. The 
quercus infectoria sometimes bear large galls known as "Ap- 
ples of Sodom" or "rove." These are caused by a different 
insect. Chinese and Japanese galls are produced by the action 
of an aphis on a kind of sumac. 

Sumac (rhus coriaria). — Sicilian sumac is obtained from 



VEGETABLE TANNING MATERIALS - 553 

a bush of which the leaves and twigs are used. The bushes 
begin to bear in the second year, but the best material is ob- 
tained from the mature bush. Cropping is done by pruning 
off the shoots or picking the leaves by hand. The leaves are 
then dried either in the field or on rocks, and are afterwards 
separated from the stems by heating. The leaves are then 
ground to a powder under edge-rollers and shipped in bags. 

Mascolino. — This is the best grade of sumac, coming from 
Palermo, while feminella is a weaker grade from other parts 
of Sicily. 

After the sumac has been submitted to the first grinding, it 
is passed through screens and the coarser particles are 
re-ground. 

Good sumac contains from 25 to 27 per cent of tannin, 
while some samples may run much higher. The tannin is 
mostly gallotannic acid, with some ellagitannic acid and a 
coloring matter. 

Sumac is the best tanning material known for light colors 
and soft leathers, and is therefore largely used in making 
Moroccos, sheepskins, and skivers. It is also largely em- 
ployed to improve the color in darker tannages. 

Rhus glabra. — This is a sumac found in the Southern Amer- 
ican States, and is largely used in place of Sicilian sumac. It 
contains about 25 per cent of tannin, but produces a much 
darker leather than that made with Sicilian sumac. 

Rhus typhina. — Known as "stag-horn," is a variety of 
sumac found in Virginia and contains from 10 to 18 per cent 
of tannin. The color produced with this sumac is nearly 
equal to that obtained with Sicilian sumac. 

In Virginia the leaves are collected and dried, but no at- 
tempt is made at selection. The leaves are usually taken when 
full of sap, sometimes being simply stripped from the twigs; 
and sometimes the whole stock is cut and the leaves are 
allowed to wither in the sun. In such cases the leaves, when 
partly dry, are transferred to sheds and spread out in a thin 
layer on a rack. The time required for drying varies with 
the weather conditions and may even take a month for a per- 



554 PRACTICAL TANNING 

feet cure. When in proper condition they should be dry and 
brittle. Although Virginian sumac is fairly high in tannic 
acid it does not produce as light a color as is obtained with 
Sicilian sumac. 

The grinding of sumac is usually done in the edge-runner 
and the resulting powder sifted to remove twigs and stems. 
French sumac is obtained from a poisonous shrub found grow- 
ing in the south of France called stinco. It is low in tannic 
acid, and although it has no tannin value, it is used mostly 
as an adulterant of true sumac. 

Gambier. — This material is derived in most part from a 
climbing shrub, uncaria gambier, found in the Dutch East 
Indies ; or from terra japonica, also known as catechu. It is 
also cultivated by the Chinese in a very crude manner. The 
first crop is taken about three years after planting and the 
leaves are taken two to four times annually, the life of the 
shrub being about 15 years. After cropping, the leaves are 
thoroughly chopped and placed in kettles with boiling water. 
Concentration, with constant stirring of the liquor, is carried 
out until a syrup is obtained. The leaves and twigs are then 
removed with a fork and the excess liquor is allowed to drain 
back into the kettle. The heavy extract is then placed in 
tubs to cool, and when in a pasty condition it is again placed 
on a flat surface and cut into cubes. These cubes, which are 
about an inch long, are placed in a shed on bamboo trays 
and dried out with wood fires. Cube gambier is dark brown 
on the surface, but pale on the inside. Its tannin is a catechol- 
phloroglucol derivative. It produces a soft tannage, and is 
much employed in the production of glove leather. The tan- 
nin content of good cube gambier is from 50 to 65 per cent. 

A more common and cheaper form of gambier is that 
known as "block gambier," which in place of being cut into 
cubes is run into large oblong blocks weighing about 250 lb. 
each. These blocks, which are of a pasty consistence, are 
wrapped in matting and shipped. Block gambier contains 
from 35 to 40 per cent of tannin. 

Modern factories have been established in Sumatra and other 



VEGETABLE TANNING MATERIALS - 555 

places, which are equipped with the latest approved apparatus 
for extraction and concentration. A greatly improved prod- 
uct is therefore available and is known as Indragiri gambier. 

Myrabolans. — This tanning material is obtained from the 
unripe fruit of the tcrminalia chebula, a tree growing to a 
height of from 40 to 50 feet. The content of tannin, which 
runs from 30 to 40 per cent, varies with the maturity of the 
fruit. Of the various kinds, the "Bombay s" are the least un- 
ripe, while the "lean greens" are the most unripe. The more 
unripe the fruit the higher the tannin content. Bombays are 
light in color and have a smooth surface skin, with coarse 
wrinkles. J's (Jubbalpores) and U's (Urigorlas) are harder 
than the Bombays and have finer wrinkles. Lean greens are 
the most unripe fruit and produce a color very closely re- 
sembling sumac. The tannin present is of the gallotannic and 
ellagitannic acid derivation. The nuts should be hard in char- 
acter and not of a waxy or soft appearance, otherwise diffi- 
culty is encountered in grinding. This softening is likely to 
happen, however, if the nuts are stored in a damp place. 

Not only does the fruit from this tree contain tannin, but 
the bark is also high in tannic acid. Extracts from the bark 
show high percentages, but they have not been introduced to 
the trade to any extent. 

Divi-divi. — This tanning material is obtained from the dried 
pods of the ccesalpinia coriaria, a native tree of Central Amer- 
ica growing to a height of about 30 feet. The pods con- 
tain from 40 to 45 per cent of tannin of the pyrogallic and 
ellagitannic variety. When used in a concentrated liquor it 
produces a heavy and firm product very desirable in the manu- 
facture of sole leather. In dilute liquors, and when used in the 
drum or paddle, it produces a very fair color on light leather. 

Algarrobilla. — This tanning material is found in Central 
America and is derived from prosopis pallida. It appears 
on the market as long pods with a fairly high tannin content. 
Some of this material has been sent to the United States as 
a mixed tanning material, but its use has not become general. 

Mimosa bark. — This bark from the acacia arabica is used 



556 PRACTICAL TANNING 

largely in India for tanning kips. It contains from 12 to 20 
per cent of catechol tannin. 

Wattle bark. — The bark is from various species of Aus- 
tralian acacia, and on account of the high tannin content, run- 
ning in some cases as high as 50 per cent, it bids fair to be- 
come a very important factor in the production of leather. 
A great deal of work has been carried out with this material 
during the past few years, and the results obtained look very 
promising. 

Palmetto. — The saw palmetto of Florida, sobal serrulata, 
contains considerable tannin in the roots, and from it an 
extract may be made which produces a light-colored leather. 
As the supply of palmetto is very large, it offers a raw 
material for extract manufacturers which should compete 
closely with some of the other common extracts, In about 
1904 an attempt was made to introduce this tanning material, 
but for some reason it did not meet with an enthusiastic re- 
ception. Recent attempts, however, have been somewhat 
more encouraging, and it is now being used successfully in 
tannage where a soft and mellow leather is required. 

Sulphite cellulose extract. — In the manufacture of wood 
pulp by the sulphite process, the ligneous matter is dissolved, 
leaving the cellulose in a fibrous condition. The liquor thus 
formed is purified by removing the objectionable constituents, 
and the resulting product is concentrated by evaporation until 
a liquor of the consistence of an ordinary tanning extract is 
obtained. 

This extract, when tested by the hide-powder method, shows 
about 25 per cent of a substance absorbed by the hide powder. 
It is not claimed by the manufacturers that' this substance is 
tannic acid, but it is claimed that this absorbable material will 
produce or help to produce leather. On account of its low 
cost and certain other valuable properties sulphite cellulose 
extract is used in large quantities with entire satisfaction. 
It may be used alone, but better leather is produced by mixing 
it with other tanning extracts. It finds its largest application 
as a filler in extract tannage of sole leather where it seems to 



VEGETABLE TANNING MATERIALS - 557 

give weight and aids in producing a light-colored product. 
A series of tests carried out by the author indicates that sul- 
phite cellulose extract may be used to advantage as a bottom 
in the manufacture of heavy leather. By so doing, the stock is 
given a light colored bottom which remains even after the 
treatment with other tanning materials. 



CHAPTER XVIII 
SYNTHETIC TANNING MATERIALS 

During the past fifty years, chemists have been endeavoring 
to produce tannic acid synthetically, but up to the present 
time their efforts have been without success. There are, how- 
ever, a number of products on the market which are spoken 
of as synthetic tanning materials, but this term is incorrect 
and misleading, as none of them bears the faintest relation to 
true tannic acid. Practically all of these compounds are de- 
rived from coal tar, and are either condensation products or 
derivatives of aromatic compounds. 

The first really important work along these lines was when 
Stiasny succeeded in changing the well-known condensation 
products of phenol and formaldehyde into a water-soluble 
compound, and showed that the product possessed tanning 
properties. This reaction is accomplished by acting upon two 
molecules of phenol-sulphonic acid with one molecule of for- 
maldehyde, and then neutralizing the resulting product with 
sodium carbonate. The product at first prepared by Stiasny 
was originally called "syntan" but on account of objection 
was later called "neradol." 

For the production of what is now sold as neradol D a 
mixture of ortho, meta, and para cresol is employed. This 
compound met with fairly general application before the 
World War, and when the German patents were taken over 
by the Chemical Foundation, it was one of those included in 
the list. Several firms in the United States are now making 
a similar product. Its chief use is as a pre-tan in the produc- 
tion of heavy leather. The hides are usually run in a solu- 
tion of this material for about 24 hours at a density of 60° 
bk., when they are transferred to strong tan liquors. Nera- 

558 



SYNTHETIC TANNING MATERIALS 559 

dol and its substitutes may also, it is claimed, be used in con- 
junction with other tanning materials. 

Not only has it been shown that phenol and cresol are 
capable of producing compounds possessing tanning proper- 
ties, but many other products have been tested with varying 
degrees of success. Among these compounds might be men- 
tioned />-amidophenol, chlorophenol, trinitrophenol, pyroca- 
techine, resorcine, hydroquinone, benzoquinone, mono-chloro- 
hydroquinone, orcine, pyrogallol, gallotannic acid, naphthols, 
naphthol derivatives, anthracene, anthracene derivatives, an- 
thraquinone, and anthraquinone substitution products. 

Some of the above chemicals produce condensation products 
having tanning properties, while others give sulphonation prod- 
ucts with marked tanning efficiency. 

From the first announcement of Stiasny's success in pro- 
ducing a substance which would transform hide substance into 
leather, chemists as well as manufacturers became interested 
in further extending our knowledge of these materials. Tan- 
ners are in a credulous state of mind, and are willing to give 
these new substances every advantage of experimentation. 
This is no doubt due to the fact that everyone realizes that 
our supply of natural tanning materials is shrinking, and we 
all appreciate the wonderful results that followed the synthesis 
of alizarine with the consequent building up of a synthetic 
dyestuff industry. 

During the World War, the Germans were forced to de- 
velop every source of domestic tanning material, and as a re- 
sult they resorted to the following materials : Spruce bark, 
chestnut wood, sumac, willow bark, birch bark, hops, pine 
bark, chestnut hulls, lentiscus, walnut bark, elder bark, and 
sulphite cellulose. They also resorted to the synthetic ma- 
terials which were sold under the names of triumphite, nera- 
dol D, neradol N, neradol ND, and ordoval, all of which are 
condensation products of formaldehyde with phenol, cresol, 
and naphthaline derivatives. These synthetic materials as 
well as others were used alone or in combination with the 
inferior vegetable tannins mentioned. 



560 PRACTICAL TANNING 

American chemists are producing many of these synthetic 
materials, and are continually endeavoring to bring them to 
a higher degree of perfection. 

An article of exceptional merit, which is recommended to 
the reader, is that by George Grasser in the January, 1921, 
Journal of the American Leather Chemists' Association. Some 
of the most striking features, however, are quoted below : 

Dihydroxybenzene (pyrocatechol) yields with sulphuric acid a sul- 
phonic acid, soluble in water, which assumes a deep blue color upon 
the cautious addition of formaldehyde. This liquid stands heating 
to 100° C. without precipitating insolubles. However, if some formal- 
dehyde is again added there follows immediately a brownish-black 
color with the precipitation of considerable quantities of insoluble 
condensation products. On the other hand, if the sulphonic acid is 
diluted a third with water, formaldehyde then added, and heated on 
the water-bath, a brown color results with complete union of the 
formaldehyde to the water-soluble condensation product. 

The tanning test with this condensation product, which was partly 
neutralized as in the above test, yielded after a 24-hour period an 
intense dark coloring of the grain, while the inner part of the pelt 
was white but completely pickled. After 48 hours more, this dark 
color, however, penetrated the whole thickness of the pelt and tan- 
ning was completed. The washed and oiled leather was soft, full, 
tough, and possessed an even gray color. 

Meta-dihydroxybenzene (resorcin) can also be easily converted by 
concentrated sulphuric acid into water-soluble sulphonic acids of 
brown color. If this sulphonation product is then diluted one-fourth 
with water, cooled down completely, treated with a few drops of for- 
maldehyde and heated on the water-bath for combination of the for- 
maldehyde, cooled down again, treated with a very little formaldehyde, 
and then heated gradually on the water-bath while stirring, a condensa- 
tion product is obtained as a mass soluble in water to a brown color. 

The usual tanning test proceeded extremely rapidly; and the pelt 
was completely tanned through in 24 hours with a light brown color. 
The lightly oiled and dried leather showed a greenish yellow color, 
was plump, tough, and soft. 

Para-dihydroxybenzene (hydroquinone) was converted into the 
water-soluble sulphonic acid with concentrated sulphuric acid at 100° 
C. ; this, treated with a little formaldehyde at ordinary temperature, 
solidified immediately to a white, solid mass, which was soluble in 
water, and which had completely fixed the formaldehyde. If this 
mass, however, was heated for a longer time at 100° C., a light brown 
color appeared and the condensation product was less soluble in water. 
A small excess of formaldehyde and moderate warming leads to dark, 
violet-colored, insoluble condensation products. 

Tanning, carried out in the usual way, proceeded somewhat more slowly 
and after a 7-day period yielded a brown-colored, tough, and soft 
but rather thin leather. 

Of the trihydroxybenzenes, only pyrogallol and phloroglucine were 
used in this investigation. Pyrogallol, upon sulphonation with con- 
centrated sulphuric acid, yielded a violet-colored, water-soluble sul- 
phonic acid, which, when treated with formaldehyde, at first while 



SYNTHETIC TANNING MATERIALS 561 

cooling and finally while warming, solidified and yielded a deep red- 
brown, water-soluble mass. 

Tanning carried out in the usual manner, yielded after 24 hours a 
dark-colored grain and white, pickled interior. The dark-colored part, 
however, penetrated the whole pelt quickly and was complete in 7 
days. The resulting leather possessed throughout a dark color, was 
plump, soft, and tough. 

In connection with the phenols, quinone may be briefly discussed, 
its use as a practical tanning material being first described in German 
patent 206,957 of April 30, 1907. According to this process, only 
400 grams of quinone are used to 100 kilograms (kg.) of pelt, and the 
pelt is tanned with it in 5 hours in a drum. Leather produced in this 
manner, in the course of tanning assumes first a red, then a violet, 
and finally a brown color, and its resistance to water, acids, and 
alkalies will be much greater than with all other known tannages. 
The chemical properties of this tannage have also given a motive to theo- 
retical consideration and according to Thuau (Coll., 1909, 363, 211) in tan- 
ning with quinone-like bodies, leather is formed by the quinone entering 
into reaction with the amido group of the protein molecule according 
to the equation: 

2R.NH 2 +2C 6 H 4 <^ = C 6 H 4 <^g + C 6 H4(O.NH.R) 2 
(hide) u uti (leather) 

Fahrion demonstrated that during quinone tannage the content of 
active oxygen in the quinone becomes smaller, and only the amido 
group of the hide protein can effect this. Dianilin-quinone might be 
named as a known analogy. 

Distinct quantities of hydroquinone can be actually detected in a 
used solution of quinone. Hide can also be tanned by saturating 
with hydroquinone and oxidizing with air. When such hide is taken 
from the hydroquinone bath and brought into the air, in the presence 
of^alkali, it is colored, first red, then violet, blue, and finally brown, 
and is converted into a quinone-tanned leather. There is still to be 
mentioned that quinone is also able to effect a pseudo-tannage. If 
quinone is left standing for a while in water, a nearly black, amor- 
phous body is formed which is almost insoluble in water, but which is 
abundantly absorbed by hide powder. However, it is not changed 
into such an insoluble form as is the case with other tanning materials. 

From the series of nitro compounds, trinitrophenol (picric acid) 
C 6 H 2 (N02)30H was investigated. If picric acid in concentrated solu- 
tion is used for a tanning experiment, the pelt is entirely penetrated 
by it in a few days. However, oiling hide tanned in such a manner is 
difficult, since the fat is poorly absorbed. After drying, a fairly soft, 
but thin leather is obtained which easily loses color and tastes in- 
tensely bitter. These disadvantages prevent the general utilization of 
picric acid as a tanning material. 

If picric acid is sulphonated with concentrated sulphuric acid and 
formaldehyde gradually added, condensation takes place to a water- 
soluble product which precipitates gelatine. By the introduction of 
bromine, however, a water-insoluble product is formed. 

Of the aromatic alcohols, the di-alcohols show a characteristic be- 
havior because they condense with sulphonic acids with the elimina- 
tion of water, without the assistance of aldehydes. Besides, mono-, 
disulphonic acids and the higher sulphonated products of phenols, the 
homologous cresols, xylenes, and naphthenes (German patent 300,567) 
also enter into the reaction. The condensation between the com- 
ponents takes place extraordinarily easily, with liberation of so much 



562 PRACTICAL TANNING 

heat that the process proceeds quantitatively. On the other hand, 
dilute solutions must be heated to 100° C. when the process is com- 
pleted in a few minutes. The products obtained are exceptionally 
pure, crystalline, and with their power of precipitating gelatine show a 
powerful capability to tan hide. The reaction is as follows: 

2 0H>C,H a CH3+HO.C,H 3 <CH : OH = 

CH2C6H 2 CH3< cr . tt 
2H 2 HO. C 6 H 3 < bU3hl 

CH2C 6 H2CH3<oq tt 

Of the aromatic acids, the behavior of salicylic acid 
(CbH 4 OH.COOH), is especially to be emphasized. This can be 
sulphonated very easily at a high temperature by concentrated sul- 
phuric acid and the sulphonated product, which forms a white solid 
mass, is soluble in water to a completely clear solution. This mass 
mixed with about one-third of its weight of water and treated at 
120° C. with formaldehyde, changes rather rapidly into the con- 
densation product. A reddish-brown liquid results, which is miscible 
with water to a clear brown solution. 

A piece of pelt placed in a 3° Be. solution of this condensation 
product was converted within three days into white, plump, and 
tough leather. Obtaining synthetic tannins from nuclear homologues 
of salicylic acid is the subject of a patent declaration (German patent 
A. 28,901). Cresotic acid ( hydroxy toluic acid, OH.C 6 H 3 CH 3 COOH), 
also gives similar results. 

Condensation of naphthalene derivitives. — As the phenol-sulphonic 
acids can undergo condensation, so also is it possible to condense 
naphthalene and naptholsulphonic acids, with elimination of water, 
to tanning substances. If naphthalene is heated with sulphuric acid, 
there is formed, at a lower temperature (about 80° C.) a-naphthalene- 
sulphonic, at a higher temperature (160° C.) and with excess of 
sulphuric acid, J-naphthalenesulphonic acid which is also formed 
by heating the a-acid with sulphuric acid. Both of these acids are 
deliquescent, crystalline substances. On longer heating of concen- 
trated sulphuric acid with naphthalene the 2.6 and 2.7 naphthalene- 
disulphonic acids are formed, while a series of isomeric naphthalene- 
trisulphonic acids are obtained by indirect means. From fc-naphtha- 
lene sulphonic acid, &-napthol can be produced ; a- and 6-naphthols in 
turn are able to form a large number of a- and ^-naptholsulphonic 
acids, and mono-, di-, and trisulphonic acids. Almost all of these 
acids represent important raw material for the production of dye- 
stuffs. 

The simplest condensation of ^-naphthalene sulphonic acid is 
attained after several hours' heating at 135° C. and 20 mm. pressure 
(Austrian patent 61,061). The product thus obtained is a cheesy 
mass which reacts very strongly acid. By neutralization of this acid 
to a lower acidity, a gray-colored cheesy mass is produced which is 
easily soluble in water to a light grayish-brown liquid. This product shows 
a good tanning action on hide. 

The condensation of b -naphthalene sulphonic acid proceeds much 
more energetically with the use of formaldehyde. For practical 
production, the naphthalene sulphonate is condensed with formalde- 
hyde at 85° C, and this condensation product forms the neradol 
N of the trade; greater dilution and neutralization brings it to the 
same tannin content (33 per cent) as neradol D, and this product 



SYNTHETIC TANNING MATERIALS 563 

appears in trade under the name of neradol ND (German patent 
290,965). Both products are capable of changing hide in a very- 
short time into a normal leather of white color. 

Besides formaldehyde other substances are able to effect a con- 
densation of naphthalene sulphonic acids. If, for example, sulphur 
chloride is allowed to act on b-naphthalene sulphonic acid, a light 
brown, solid mass of strongly acid character is obtained. _ This, 
neutralized as usual, produces a grayish-brown solid mass, which is very 
easily soluble in water to a light-brown liquid. A tanning experiment made 
with this solution yielded a light-brown and fairly soft leather. 

/4-naphthol dissolved in hot concentrated sulphuric acid and heated 
for some time on the water-bath forms o-naphthol sulphonic acid. 
This, moderately diluted with water and mixed cold with formalde- 
hyde, shows no change. On warming the mixture on the water-bath 
a brown precipitation occurs. This turbid liquid treated with gelatine 
produces a heavy flocculent precipitate. If the turbid solution which 
has been heated on the water-bath is treated with caustic soda, 
then solution is effected with the formation of a light yellow liquid, 
which also remains clear after the addition of an excess of acetic 
acid and gives a heavy precipitate with gelatine. The hot concen- 
trated a-naphthol sulphonic acid treated with sufficient formaldehyde, 
effervesces violently and yields a dark brown insoluble condensation 
product which is soluble in caustic soda. This alkaline solution 
treated with an excess of acetic acid, also precipitates gelatine 
copiously. 

If &-naphthol is dissolved in hot concentrated sulphuric acid and 
heated for some time on the water-bath, a brown, viscous solu- 
tion of &-naphthol sulphonic acid is formed. This, moderately diluted 
and mixed with formaldehyde, remains clear, but is colored to a 
dark reddish yellow by heating on the water-bath; however, it 
remains soluble in water and is abundantly precipitated by gelatine. 
This condensation product, super-saturated with caustic soda, yields 
a deep blue solution, which does not precipitate gelatine; on the 
addition of acetic acid it is colored brown and remains clear and 
will then precipitate gelatine copiously. If concentrated 6-naphthol 
sulphonic acid is heated on the water-bath with formaldehyde, a 
condensation to a dark reddish-yellow, water-soluble mass occurs 
which will give a copious precipitate with gelatine. 

The action of these condensation products in moderately concen- 
trated solution yielded in a few days a light-brown leather which is 
very similar in its properties to vegetable-tanned stock. 

The practical utilization of the production of synthetic tannins 
from naphthols and aminonaphthalene sulphonic acids is protected in 
German patents 293,042, 293,640, 293,693, and 303,640. 

In a recent article which appeared in Ch.imie et Industrie, 
vol. 11, page 1024, and translated in the Journal of the Amer- 
ican Leather Chemists' Association for February, 1920, Pro- 
fessor E. Nihoul gives a full description of synthetic tanning 
materials and among others mentions the use of quinone as a 
tanning agent as follows : 

Quinone: its action on gelatine and hide. — In 1908, Meunier and 
Seyewetz published results of their researches upon the rendering 
insoluble of gelatine by the action of the following organic com- 



564. PRACTICAL TANNING 

pounds: Phenol, resorcinol, orcinol, hydroquinone, pyrocatechin, gal- 
lotannic acid, pyrogallol, />-aminophenol, chlorophenol, picric acid, mono- 
chlorhydroquinone and the mono- and disulphonic acids of beta-naphthol. 

The phenols only slightly soluble in water, such as alpha- and 
beta-naphthols, as well as the simple and substituted amines and 
aminophenols, either when existing in salts or as free bases, do not 
give precipitates with gelatine solutions. But if conditions are 
provided favorable to oxidation, both phenols and aminophenols 
give precipitates which are insoluble in boiling water. This fact led 
the investigators to experiment with oxidation products of the phenols, 
especially ordinary quinone. They discovered that the gelatine 
quinone precipitate is the most stable form of insoluble gelatine at 
present known, for it resists not only the action of boiling water, 
but even of dilute acids and alkalies. The time required to render 
gelatine insoluble by means of quinone is less than two hours at 
15° C. The quinhydrones react similarly, only more slowly. On the 
other hand, experiments with formaldehyde gave a product which 
dissolved completely under repeated treatment with hot water and 
which slowly lost formaldehyde when subjected to dry heat. Further- 
more it is dissolved in the cold by hydrochloric acid and dilute 
alkalies. 

The same results were obtained with hide as with gelatine, either 
with phenols and aminophenols in the presence of oxidizing agents, 
or with quinones without oxidation. 

Comparative experiments with other substances capable of reacting 
with hide substance show that a liquor containing only 1 part of 
quinone per 100 parts by weight of raw -pelt renders the latter 
insoluble, transforming it into a leather whose resistance to the action 
of water, acids, and alkalies is superior to that of any other leather 
known — chrome leather included — and whose resistance to wear is at least 
equal to that of the best leather tanned with oak bark. 

The analysis of used quinone liquors reveals the presence of 
hydroquinone, which proves that a part of the quinone was used 
to oxidize the hide substance, while the remainder entered into a 
stable combination with the oxidized hide. Since hydroquinone is 
readily oxidizable, the yield will be greater if means are provided 
to re-oxidize it. The provision of conditions favorable to oxidation 
favors this tannage, and the use of catalyzers, such as the laccases, 
artificial peroxidases, and acetates of Mn, Ce and La, consequently 
produces a better and more rapid tannage. Meunier has pointed out 
that oxidases are to be found among the soluble matters given up 
by the hide during tanning. 

Methods of preparation and properties of quinone. — In general, quinones 
can be obtained' by oxidation of the corresponding paradiphenol compounds 
and can also be produced when more than two hydroxy groups are 
present, provided two of these groups are in the para position. They 
are formed likewise by oxidation of numerous compounds derived 
from the phenols such as />-phenol sulphonic acid and />-aminophenol, 
but the method often employed in laboratories is to oxidize, by means 
of chromic acid, certain mono-substituted derivatives of benzene, 
such as aniline. 

Among the chief properties of quinone of interest to the tanner 
are the following: It is soluble in cold water to the extent of only 
about 0.5 .per cent., but dissolves to a considerably greater extent 
in warm or acidified solution. In practice, it is dissolved in slightly 
acidified boiling water, but this should be done in a closed tank, as 
the product is volatile and easily carried away in the vapor. Acid 
solutions are stable for a much longer period than neutral or alkaline 
solutions, and light is harmful in causing oxidation, Quinone 



SYNTHETIC TANNING MATERIALS 565 

solutions should not be brought into contact with metals nor put 
into wooden vats which have been used previously for vegetable 
tannins, as they will darken in color and lose their property of 
giving a clear tannage. Quinone is readily kept in the crystalline 
state either in wooden or tinned containers. It is dissolved only as 
needed and not more than will dissolve. 

Application in the tannery. — Quinone alone, employed to the extent 
of H parts to 100 of pelt, is capable of completely tanning the stock 
in a few days. It would therefore seem at first sight that quinone 
tannage constitutes an ideal process -both from the standpoint of 
speed and of cost. In reality this is not the case, and the reason lies 
in the fact that the leather is sold by weight, a procedure which was 
established in times past, when hides sold at a price reasonably 
higher than that of tannin, in order to induce the manufacturer to 
get enough tannin into his leather to ensure complete tannage. Since 
then the situation has changed, and hides have increased in price out 
of all proportion to that of tannin. The result of this has been, 
especially in the case of rapid tannages, an increase in proportion of 
tannin, combined or not, in the leather, until now some of the better 
grades often contain not more than 30 to 35 per cent of hide 
substance. 

It is quite evident that under these conditions tanning with 
quinone alone cannot compete with tanning with vegetable extracts, 
excepting for light leathers sold by the square foot. Nevertheless, 
on account of its great value as a preliminary tanning agent, it 
has become an article of considerable importance. Before the ap- 
pearance of quinone, formaldehyde was employed preliminary to 
vegetable tanning, with the object of isolating and strengthening the 
hide fibers so as to enable the hide to be put into concentrated 
liquors without harm. But the formaldehyde does not remain fixed, 
and experience has shown that after storing for some months these 
leathers undergo change, becoming hard. No such difficulty is found 
with the use of quinone, and hides first treated with quinone fix 
vegetable tannins with remarkable speed, without any disadvantage either 
to the leather or to the modern methods of rapid tannage. Further- 
more, its use has increased rapidly in the manufacture of all kinds of 
leather, particularly sole leather. 

The Leather World of March 10, 1916, devoted considerable space 
to the use of quinone as a preliminary tanning agent. It has been 
used for sole and strap leathers, where it has been demonstrated that 
such leathers possess greater resistance to wear than others not so 
treated. It has also been used for upper leather and has even been 
employed with chrome leather. 

For box calf it is best not to shave the skins too deeply after 
the beam-house work, the quinone giving them sufficient suppleness. 
The operation consists in adding to a soak of 100 kilos of skin 600 
grams of quinone and 300 grams of 80 per cent lactic acid. If 
the stock has been bated, the acid is unnecessary. For ordinary 
leathers, acetic acid is preferable. The tannage is then carried out 
with a one-bath chrome liquor, using only 60 per cent of the usual 
amount of chrome and neutralizing agent. Box calf made in this 
way is better than the ordinary in that it is more permeable to air 
and gives a shoe which is more hygienic and cooler in Summer; it 
is more supple and has a finer grain; and in dyeing, the black is 
distributed more uniformly, not only over each skin, but over all 
skins in the same lot, thus increasing the number of first-grade 
skins. When used for colored calf, the proportion of sumac and 
gambier can be greatly reduced and the grain is never hard or brittle. 
The same holds true for smooth calf, whether black or colored. 



566 PRACTICAL TANNING 

Preliminary quinone treatment of kidskins intended for shoes makes 
possible the use of one-bath liquors and makes the sorting for colors 
unnecessary. 

During the past two years attention has been called to 
the use of several other organic compounds which possess tan- 
ning properties and which promise to open up a new field for 
the preparation of synthetic bodies for leather manufacturers. 
Most of the compounds are sulphonated products of the higher 
hydrocarbon compounds. 



CHAPTER XIX 
UNUSUAL TANNING PROCESSES 

Electric tanning. — The first attempt to utilize electricity 
as an aid to tanning was by Crosse in 1850. Later, Ward 
continued the researches of Crosse, but without any marked 
success. From time to time since that date investigations 
have brought out new suggestions, but they all depend upon 
electrolysis of the tanning solution. 

The first process which was at all successful was intro- 
duced by Meritens in 1874. In this process the usual tan- 
ning solutions were employed. On the bottom of the pit was 
placed a plate of graphite connected to the positive pole, the 
hides were entered, and a zinc plate was placed in the top of the 
solution. The zinc plate was connected to the negative pole and 
the current allowed to pass through the liquor, a regular 110- 
volt current being used. Tanning by this treatment was said to 
be complete in 35 days. The cost of the current in this process 
is an item which must be considered, and unless it can be ob- 
tained cheaply it is prohibitive. 

Although other attempts were made, the next large-scale 
experiments were undertaken in Sweden, when an alternating 
current was employed and copper electrolysis used. The time 
required was 45 days. In 'this process the hides were sus- 
pended parallel to the electrode. The current was thus caused 
to pass through the hides. 

A process devised by Worms and Balle consists in the use 
of ordinary drums. On the inside of the drum, on opposite 
sides, were placed copper disks connected by rods to the source 
of current. From 1000 to 1200 lb. of hides were placed in 
the drum and about 75 gallons of chestnut liquor added, and 
the drum set in motion. Through the trunnion 1^ gallons of 
oil of turpentine was introduced, and the current turned on. 

567 



568 PRACTICAL TANNING 

The intensity of the current was 10 amperes with a tension 
of 70 volts. The tanning bath was strengthened from time 
to time. When well struck through, the current was turned 
off and the drum run for another interval. 

It was claimed that bull hides could be tanned in 5 or 6 
days by this process, while lighter hides required a shorter 
period. 

A process devised by Place consisted in placing the hides 
in closed vats provided with agitators, and along the bottom, 
a series of comb-like conductors. The hides were placed in 
the vats containing a liquor standing at about 5° Be. The 
first treatment extended over a period of 8 hours with an in- 
tensity of current of 20 amperes. The hides were then thrown 
into another vat with 5° Be. liquor, but no current was passed 
through the liquor. Agitation, however, was employed, and 
the process for the heaviest hide was complete in about 100 
hours. 

Although other processes have been and still are constantly 
being suggested, no process has as yet been sufficiently success- 
ful to warrant serious consideration. 

Vacuum tanning. — Many attempts have been undertaken 
to make this commercially feasible, but up to the present time 
none of the vacuum processes have met, with success. 

Seymour-Jones method. — By this method the de-haired 
and washed hides are placed in a 0.5 per cent solution of for- 
maldehyde, where they are allowed to remain 4 days. The 
grain is then fixed by placing on frames in liquor of mixed 
tanning material standing at 45° bk., a rocker system being 
employed. The hides remain in this liquor for 48 hours. They 
are then transferred to a drum and enough liquor at 75° bk. 
to cover the stock is introduced. A small quantity of turpen- 
tine is added to prevent frothing. After the hides have been 
entered the drum is set in motion and run for 2 hours. The 
door is opened and the drum allowed to remain at rest for 
4 hours. It is then run again for 3 hours and allowed to 
rest over night. The next day the drum is run in the same 
manner as on the first day, when by night the stock should be 



UNUSUAL TANNING PROCESSES 569 

tanned through. The hides are dried in a fairly warm room, 
sammied, scoured, oiled off, and dried in the cold. They are 
then re-tanned with strong extract in a mill, running for 15 
minutes. The hides are next oiled off with a sulphonated oil 
on the grain and again set-out. Another coat of oil is ap- 
plied and the stock dried in a cool loft. When dry, they are 
waxed, rolled, and finished. 

This method is especially successful on heavy calf and is 
claimed to be applicable to heavy hides as well. 

Organ leather. — The principal uses of leather in the manu- 
facture of organs have been thoroughly investigated by the 
United States Bureau of Standards, and are as follows : 

1. Bellows 

(a) Gussets 

(b) Hinges 

(c) Valves 

2. Pneumatic pouches or diaphragms 

3. Pneumatic valves 

Alum-tanned sheepskin appears to be used by most manu- 
facturers for bellows, gussets, and hinges. Leather for the 
hinges of the folds of the bellows is required to be firm and 
well stretched. A soft, pliable, unstretched leather is required 
for the gussets or corners where it is necessary that the leather 
fold in or out as the bellows move up or down. It is neces- 
sary that the leather be free from any groan or squeak while 
in motion. 

A small, rectangular piece of leather is used for bellows 
valves. This leather is held over the valve-opening in the side 
of the bellows by tacks or a strap. The leather should be 
firm and well stretched so that it will lie flat and not curl 
up on the edges. Bark-tanned sheepskins, chrome-tanned 
cowhide, and chrome-tanned calf are used for this purpose. 

For box or pouch pneumatics, sheep or lambskin skivers 
are generally used. A skiver is defined as the grain split 
of a sheep or lambskin. The split is taken off when the skins 



570 PRACTICAL TANNING 

are in the rawhide state. These are mostly vegetable-tanned, 
but occasionally some alum-tanned skivers are used. 

A variety of leathers are used for pneumatic valves. The 
most common are alum-tanned and chrome-tanned calf or 
cowhide leather. Some sheep and goat leathers are also used. 

For miscellaneous joint packings, bark-tanned or chrome- 
tanned sheep fleshers are generally used, while in some cases 
seal fleshers are employed. 

Leather for player-pianos. — The uses for leather in player- 
pianos follow the same general classifications as described 
for organs, the chief difference being the leathers used on the 
pneumatic valves. While a variety of goat, sheep, cowhide, 
and calf leathers are used, the most common is chrome calf 
re-tanned in a vegetable-tanning material. Leather used for 
this purpose should be firm, similar to calf for shoe uppers. 
The flesh side generally rests on the valve-seat, which is metal, 
and forms an air-tight joint. The grain side is glued to a 
wooden disk on the valve-stem and is preferably napped to 
facilitate the gluing. This leather should be free from acid, 
as, if this is present, corrosion of the valve-seat may occur, 
causing sticking. It should also be dry to prevent sticking to 
the valve-seat, which thus prevents the quick and positive 
action necessary for successful operation. 

Any kind of leather that will not harden in hot climates, 
will not stick to the valve-seat, does not contain acids which 
cause corrosion of the valve-seat, and is firm, can be used 
satisfactorily on valves. No definite standard has been 
adopted, and the same manufacturer often uses different kinds 
of leather, according to what may be obtained to the best 
advantage. 

Pneumatic pouches. — Manufacturers have experienced their 
greatest difficulty in securing leather of the desired qualities 
for use on pneumatic pouches. Sheep or lambskin skivers 
are almost universally used for this purpose. 

Briefly, the operation of the action of a player-piano may 
be described as follows : Air is pumped in from the room 
through the openings in the tracker-bar and is exhausted into 



UNUSUAL TANNING PROCESSES 571 

the room through the bellows valve. When one of the per- 
forations on the music-roll passes over its corresponding open- 
ing on the tracker-bar, air is pumped through a tube or duct to 
a chamber directly beneath the pneumatic pouch or diaphragm. 
This causes the pouch to be raised. A small cardboard disc 
mounted on the center of the pouch engages with the valve- 
stem, raising it, together with the leather disc, which has been 
seated on the valve. This action allows the air to be exhausted 
from the small wing-bellows by suction, which causes the bel- 
lows to collapse. The collapsing of the bellows in turn allows, 
through suitable mechanical devices, the particular note to be 
sounded. When the opening on the music-roll has passed 
over its opening on the tracker-bar the suction is relieved, the 
pouch falls, the valve is closed and the wing-bellows fills again 
with air. 

It will be seen that this leather diaphragm is a most im- 
portant part of the action. If it is too tight, stiff, heavy, or 
leaky, the valve movement will lag and difficulty will be 
experienced. 

A skiver for this purpose must be soft, pliable, light in 
weight, uniform in thickness, and as free as possible from 
"pin-holes" or larger openings. It is not required to -be air- 
tight, and leather of this type is naturally porous on account 
of the holes left when the wool is pulled. These holes are 
partly filled in the process of manufacture, but there are 
often many holes remaining through which light is plainly 
visible, and which would allow a sufficient volume of air to 
pass so as to affect seriously the positiveness of the action. 
On this account the skivers are carefully examined in the 
factory and those portions unsuitable eliminated. 

It is difficult to secure skivers tight enough and of the 
thickness desired. On some small pneumatics skivers not 
more than 5/1000 or 6/1000 of an inch thick are required, 
while on larger pneumatics the thickness may reach 10/1000 
or 12/1000 of an inch. 

The leather must also be soft and stretchy, as it is formed 
into a pouch by a mold of spherical shape. The pouch is then 



572 PRACTICAL TANNING 

placed over the chamber in the player-board and the edges 
are glued to the board. 

The quality of a skiver is entirely dependent upon the type 
of sheey from which it is taken. The nearer the animal is 
to a hair type the better the skiver will be, in that it will be 
finer grained and will have smaller pores or hair-holes, which, 
of course, will make it tighter. 

The majority of the sheep are of the fine, heavy-wooled 
merino type, or closely approaching it. In order to allow 
sufficient space for the wool to grow on fine-haired sheep, 
nature provides ridges on the pelt so that it resembles a cor- 
rugated surface. These ridges are so high that they affect 
the quality of the leather produced and make it impossible to 
secure a skiver from these pelts suitable for piano manufac- 
turers. Thus, the original source of skins for suitable skivers 
is from animals of the hair type, which, as a rule, are ob- 
tained from foreign countries. 

Skins imported for this purpose are preserved by pickling, 
and are split after having the pickle withdrawn, but still con- 
tain some sulphuric acid which cannot be eliminated from the 
fiber. This necessitates the use of tanning liquors of such 
nature as to make the resulting leather feel" relatively harsh. 
Foreign manufacturers can split the fresh skins directly in the 
limes and then drench or "puer," as the case may be, and 
send the splits directly to -the tanyard. So-called '"sweet liq- 
uors" can be used, thereby producing a soft and pliable leather. 
It is believed that there is no factor in the working of the 
pickled pelts in the United States which would produce pin- 
holes in the leather. The question of obtaining compara- 
tively tight skins is chiefly a matter of selection. England 
splits more lambskins than are split in the United States, and 
thus has a larger volume of skins from which to make a 
selection. Also, there are tanners in England who make a 
specialty of preparing leather for the organ and piano trades, 
while in America no tanner does this on any large scale.. In 
order to emphasize the importance attached to the selection, 
one manufacturer states that out of an annual production of 



UNUSUAL TANNING PROCESSES 573 

75,000 to 100,000 dozen skivers, he would not feel safe in 
offering over 1000 dozen suitable for use in piano actions. 

The volume of business represented by the use of skivers 
in this industry has been considered relatively small It is 
probable that the largest manufacturer would use about 2000 
dozen per year, while the smaller manufacturer would use 
only 100 dozen per year, or even less. If the total were 
known it would probably represent a sizable volume of busi- 
ness. The American tanner generally, therefore, has not 
thought it worth while to solicit this business on account of 
its relatively small volume. Considerable work would be re- 
quired in making the necessary selection, which would add to 
the cost. On -this account it has been thought that the Amer- 
ican tanners cannot compete with foreign tanners on the same 
price basis for the same quality. 

Substitutes. — Rubberized fabric has replaced leather for 
covering bellows and pneumatic wing-bellows. This material 
possesses the advantages of being uniform and air-tight 
when first placed in use. It is necessary, however, to replace 
these fabrics, which fail in from 3 to 10 years' time, according 
to the operating and atmospheric conditions. This failure is 
due to the deterioration of the rubber which cracks and thus al- 
lows air to leak through. 

A very thin, rubberized silk has been tried for pneumatic 
pouches in place of skivers, but its use was not successful. 
Its life is short, and in time the rubber coating hardens, thereby 
causing a loss in pliability. Leather is ideal for this pur- 
pose, and if the quality is right, it will last a lifetime. 

The use of tanned cattle guts has been proposed, and some 
alum-tanned colons have been used. One manufacturer states 
that the alum-tanned guts are so affected by moisture that 
they dry out as tight as drumheads. One supply dealer has 
produced a vegetable-tanned colon which, it is claimed, will 
retain its pliable condition. This material is produced only 
in small pieces about 8 by 16 inches. It possesses the distinct 
advantage, however, of being practically air-tight under the 
pressures used in the instruments. Some difficulty has been 



574 



PRACTICAL TANNING 



experienced in making and gluing pouches from this material, 
but it is believed a little study and care in handling will 
obviate this objection. The possibility of the use of whale and 
porpoise intestines is now being investigated. 

The author has developed a process for making leather 
from the so-called bung gut, which answers all requirements 
for piano leather and is being favorably regarded by the trade. 

Shark-skin leather. — For several years the author has been 
interested in the utilization of shark and porpoise skins for 




Figure 120. — Hauling in netted sharks. 



leather manufacture, and has investigated the methods of 
handling this class of raw material. Through this work he 
became acquainted with Alfred Ehrenreich, president of the 
Ocean Leather Co., who has also spent many years in the study 
of this subject, and through whose efforts the establishment 
of an entirely new industry has been made possible. 

During several recent visits to the Everglades of Florida 



UNUSUAL TANNING PROCESSES 



575 



and to Morehead City, North Carolina, the shark and por- 
poise have been studied in their native haunts, and the fact 
demonstrated beyond a doubt that it is possible to handle 
these fish in a commercial manner. As a result, the 
Ocean Leather Co. has now in operation at Morehead City 
a modern plant where the hides are removed and salted. In 
addition, the livers are rendered for their oil and the flesh is 




Figure 121.— Roping a shark. 



Figure 122.— -Landing a shark. Note 
skins on pier. 



converted into a high-grade fertilizer stock. Another station 
at Sanabal Island, Florida, is also operated by the same 
company. 

Catching and handling. — The sharks are caught in nets of 
3-inch mesh, 360 yards long and about 12 feet deep. As the 
boat picks up the buoy, one man standing in the stern pulls 
in the cork line, (figure 120), while another hauls up the lead. 
When the shark is brought up, a rope is placed over the tail 
(figure 121), or, in some cases, a hook is placed in the mouth. 



576 PRACTICAL TANNING 

If the fish is alive, it is killed by a sharp blow with an axe, 
and then lifted on board by means of a block-and-fall. In an 
average haul from 10 to 20 sharks are taken from each net. 

On arriving at the dock, the fish are unloaded (figure 122), 
and the work of dressing is started at once. The first opera- 
tion is to remove the fins and tail. The former are tacked on, 
a rack and allowed to dry in the sun; they are used by the 
Chinese for making soup. The fish is then cut down the back, 
and a circular cut made over the neck and around the gills. 
The skin is finally removed in such a manner that only the 
holes of the pectoral fins and rectal opening remain in the 
pelt. The flayed skins are placed in salt for 24 hours, fleshed 
on the beam or machine, and placed in bundles for shipment 
to the tannery. 

The livers are thrown into barrels, where they are al- 
lowed to remain for several days to disintegrate, and are then 
placed in steam- jacketed kettles and heated to boiling for 
about an hour. From the kettles the oil is run into washing 
and settling tanks, where the gurry is separated from the oil. 
The oil is then drawn into a second tank, again washed, and 
finally run to a third tank, where it is stored until ready for 
shipment. Exposure to the sun and rain effects more or 
less bleaching. 

The carcass at present is used in the manufacture of fish 
scrap for fertilizer stock. Briefly, it is thrown into the 
hopper of a specially designed mill, where the flesh and bones 
are ground to a fine pulp, which is dried in a rotary dryer. 
This grade of fish scrap contains on an average 15 to 17 per 
cent of nitrogen expressed as ammonia. 

Treatment of skins. — The shark skins as they arrive at the 
tannery, are soaked in water to remove the salt and are again 
fleshed. Skins for bag leather are limed and bated in the 
usual manner and tanned in bark. The tanned skins are then 
treated to remove the shagreen, and after washing and color- 
ing are ready for the finishing process. 

The skins to be used for shoe leather are not limed or 
bated, but are at once treated for the removal of the sha- 



UNUSUAL TANNING PROCESSES . . 577 

green. This so-called shagreen is a hard layer which covers 
the whole fish ; it has the appearance of coarse sand paper, 
and is almost impossible to remove by mechanical means. The 
elimination of shagreen from the raw skins is a problem which 
has remained unsolved until recently. A process developed 
by the author consists in soaking the skins in an acid solution 
which accomplishes the removal of the shagreen in about two 
hours. By leaving skins in this solution for a week no dam- 
age is done. The skins are neutralized in a salt solution, to 
which soda ash is added from time to time. When free from 
acid the stock can be tanned by any of the methods now in 
vogue. 

Porpoise leather. — Although porpoises are not as plentiful 
as sharks they deserve brief mention. Porpoises travel al- 
most exclusively in schools, and are, therefore, usually caught 
in the purse seine (net). The method consists in surrounding 
the fish and then landing them on the beach. These fish vary 
in size from 3 to 30 ft. Their skin carries a heavy layer of 
blubber, which is split off and rendered to obtain lubricating 
oil. On the face of the porpoise is an extra heavy blubber 
known as junk, which, when rendered separately, yields a 
more valuable oil than ordinary blubber oil. In the jaw cavity 
is about 1 oz. of oil, known as jaw oil. This oil is carefully 
rendered and brings from $30 to $80 per gallon. 

The top layer of hide from which the blubber has been 
split is limed to remove the rubbery surface and open up 
the fiber bundles. It is then tanned by either the oil or the 
vegetable process as applied for other kinds of leather. 



CHAPTER XX 

ARTIFICIAL LEATHER, DOPE SPLITS, AND PYROXYLIN 

FINISHES 

Pyroxylin. — The application of pyroxylin finishes to cloth 
and leather has become a very important industry. This sub- 
ject was well set forth in a lecture by Gillett Wyncoop, of the 
Anderson Chemical Co., before the tanning and leather chem- 
istry students of Pratt Institute, Brooklyn, N. Y. 

The uses of pyroxylin for coating fabrics, leather, and pa- 
per materials is an industry which has grown largely within 
the last 20 years. A chemist in England discovered that by 
mixing pyroxylin with castor oil or various other oils, and 
putting certain colors, either dyes or pigments, in the solu- 
tion, coating this on a fabric, and then running it through a 
roller with a certain pattern engraved on it, gave a fabric 
which looked much like leather. It was pliable and did not 
crack easily, was waterproof, and would stand a great deal of 
wear and exposure to the atmosphere. About the same time 
certain industries in Newark, N. J., discovered these same 
properties, and in this manner began the manufacture of arti- 
ficial leather and finished splits. 

In the manufacture of artificial leather, pyroxylin, as a 
rule, is dissolved in a mixture of alcohol and amyl-acetate 
in about the proportion of 1 to 1| lb. of pyroxylin, according 
to the grade of artificial leather desired, to a gallon of solvent. 

Solvents. — One reason why the use of pyroxylin did not 
receive recognition earlier was on account of the solvents 
used in its manufacture. There were a great many solvents 
for pyroxylin, but few that would make a good film. Nearly 
all of the ethers, alcohols, aldehydes, and some of the hydro- 
carbon oils are solvents for pyroxylin, but only a few give 
proper results. Among the best solvents should be mentioned 
amyl-acetate, acetone, acetone oil, butyl-alcohol, ethyl-alcohol, 

578 



ARTIFICIAL LEATHER _ 579 

and methyl-alcohol. As a rule, however, a mixture of two 
or more of the above solvents is used rather than a single 
compound, a favorite mixture being amyl-acetate, acetone, 

and wood alcohol. 

To dissolve cotton in wood alcohol it is necessary to have 
a grade of alcohol that is at least 94 per cent. 

There are a number of substitutes for amyl-acetate, how- 
ever, which can be used to advantage. One of the most ex- 
tensively used today is ethyl-acetate. It has a boiling point 
near grain alcohol, around 79 or 80°, and if a solution is ap- 
plied to leather or imitation leather, and the film is warmed 
by placing over hot pipes, the ethyl-acetate will attract very 
little moisture and thus will work satisfactorily. But unless 
it is 100 per cent pure it has' little use as a substitute for 
amyl-acetate in dope finish. It is employed, however, fairly 
extensively in the artificial leather industry where goods, after 
spreading, are run over steam pipes or run through a chamber 
in which a blast of hot air is driven. 

Ketones 'are very active solvents for the cotton, and will 
dissolve the cotton quicker than any other substance. Acetone 
is the most rapid solvent, but in practical use it is unsatisfac- 
tory, on account of its low boiling-point, about 56°, and quick 
evaporation. It will evaporate before the goods can be spread. 
All of these solvents may be cheapened somewhat by dilu- 
tion with naphtha or benzene. Pure amyl-acetate will stand 
nearly 50 per cent dilution with naphtha or benzene and still 

be a solvent. 

Procedure.— After the pyroxylin is dissolved in the amyl- 
acetate and wood alcohol, a certain amount of castor oil or 
other oils is added (in artificial leather about 1-| to 2 lb, of 
castor oil to 1 lb. of pyroxylin is added to the solution). 
They are either dissolved separately and mixed or all are dis- 
solved together. After the oil is added the color is intro- 
duced. In artificial leather the color should be a dry insolu- 
ble pigment. There is nothing especially objectionable about 
the dyes except that they are likely to "crock," that is, when 
rubbed with a wet cloth the color will rub off. 



580 PRACTICAL TANNING 

In the United States there are 8 or 10 large manufactur- 
ers of artificial leather. The pyroxylin solution is spread on 
all grades of material, some not much heavier than cheese- 
cloth, up to heavy cloth weighing 2 lb. to the yard. At the pres- 
ent time some of these higher grades of cloth with a heavy 
coating are being used for even such high-grade leather sub- 
stitutes as automobile cushions, but the chief use of artificial 
leather is for upholstering for indoor work. It can, how- 
ever, be substituted for nearly every use to which leather is 
put, but, of course, is used as a cheaper product. It will wear 
as a rule as long or perhaps better than some of the cheaper 
grades of leather. 

Acid formula. — Pyroxylin is a low-nitrated guncotton. In 
its manufacture not quite as strong an acid mixture is used as 
for the guncotton employed for explosives. The acid formula 
employed in making pyroxylin, that is, the grade which is 
used for artificial leather, is about 60 per cent sulphuric acid, 
21 per cent nitric acid, and 19 per cent water. 

This may be varied in a number of ways to suit the con- 
ditions and qualities' of the pyroxylin required, for nearly 
every industry requires a slightly different grade of pyroxylin 
as to solvents and what is termed "viscosity." The higher 
the temperature at which it is nitrated the higher the viscosity. 

Anything much under the percentage given will not dis- 
solve cotton. Methyl-alcohol, or wood alcohol, has little effect 
on soluble cotton when it is absolutely pure. In technical 
work we usually specify to the manufacturer of the wood al- 
cohol that it shall contain 10 to 15 per cent of acetone, this, 
as already stated, being one of the best solvents. 

The general division of soluble cottons is as follows : A 
cotton that is insoluble in ether and alcohol or a mixture of 
the two (the latter is the old solvent that has been used for 
50 years or more in making what is known as collodion solu- 
tion), is classed as guncotton. In other words, guncotton is 
insoluble in ether and alcohol solution. This mixture can 
vary from 1 to 3 parts, respectively, or up to 3 parts to 1, re- 
spectively. The nitrated cotton is roughly divided into gun- 



ARTIFICIAL LEATHER 581 

cotton and soluble cotton. A cotton with a high percentage 
of non-soluble is classed as insoluble cotton. Cotton of less 
nitration, soluble in ether, is called collodion cotton or pyroxy- 
lin. The dividing line is not distinct. Certain cottons, when 
highly nitrated, are soluble in this solution, whereas perhaps 
nitrated in another way with slightly less nitrogen in the 
cotton would not be soluble. 

The coatings on cloth for making artificial leathers are pro- 
duced in various colors. They are finished bright and dull, 
the treatment for obtaining the bright finish being the same as 
in finishing bright leather; that is, varnish is applied after the 
last coat and a bright finish thereby produced. 

Coating real leather. — This industry started about 20 
years ago. At that time a firm at Newark, N. J., which was 
coating a large amount of leathers, shipped several carloads 
of the coated hides to their customers, and when the users 
tried to unwrap the packages they could not be cut apart with 
an axe. The hides were ruined. This practically killed the 
use of pyroxylin on splits for a number of years, and only 
recently have the tanners been willing to run the chance, as 
they expressed it, of using pyroxylin instead of japan for fin- 
ishing their hides or splits. 

Improper coating was the cause of the hides sticking, or 
the introduction of some oil that should not have been em- 
ployed with the pyroxylin. There are various oils even now 
used in the trade, such as boiled rape-seed oil or boiled linseed 
oil. It is believed by many that neither one of these oils 
should be used in a pyroxylin coating for the reason that lin- 
seed, being a drying oil, will cause the goods to crack; rape- 
seed oil is perhaps not so dangerous, and may last very well, 
but in any case there is a question, and most manufacturers 
are afraid to take a chance. 

It is well known, however, that castor oil will stand almost 
indefinitely, as it is a non-drying oil. It is true that goods 
coated with pyroxylin to which castor oil has been added, if 
kept rolled up, will sometimes dry out and something hap- 
pens to the oil, and the goods will crack, snapping almost like 



582 PRACTICAL TANNING 

a match. However, that does not often occur, and only when 
kept rolled up for a long time away from contact with the air. 
If these goods that have gone bad are again given one or two 
coatings of pyroxylin, they will become as soft and pliable and 
as tenacious as they were before. 

In making a pyroxylin for the split leather trade, the solu- 
tion used is considerably thinner than the ordinary solutions, 
because splits have to be coated by hand with a swab and 
the liquor cannot be spread as easily or as economically under 
these conditions. In split leathers, the common method for 
the first coat is to use a soft, heavy brush, 2\ in. wide and 
about 6 or 7 inches long, with a strap over it. This is dipped 
into the solution and passed evenly over the goods ; the hides 
are hung on a pole, preferably in a warm room, free as pos- 
sible from moisture, as this is the one element that gives the 
greatest trouble in working with solutions of pyroxylin. 

For the first coat an 8 to 12-oz. solution is used. Splits 
often have a heavy nap on them, and a thin solution spread 
over will leave the nap standing; whereas a heavy solution 
without putting nearly as much on, will, as it were, cement 
the nap down. The heavier the solution the less solvent is 
required, a saving, as the solvent is simply a carrier. 

For the first coat on such leather, therefore, it is well to 
use a 12-oz. solution. With this should be mixed for each 
gallon, 3J lb. of oil, according to the softness of the leather 
desired. The usual run of split leather is employed for or- 
dinary carriage cushions, upholstery, etc. The color of most 
of the hides coated with pyroxylin is black, this color requir- 
ing 2 lb. of dye to about 50 gallons of the solution. Pigments 
can be used, but as few tanners have proper mills for grinding 
them, dyes are more commonly used. An advantage in dyes is 
that they remain in solution almost indefinitely, whereas 
when pyroxylin is mixed with pigment it is necessary to keep 
stirring continually to prevent the pigment from settling out. 
Having prepared a 12-oz. cotton solution to which 3 lb. of 
castor oil and 2 or 3 oz. of a soluble dye has been added for 
each gallon, it is spread over the goods in a warm, moisture- 



ARTIFICIAL LEATHER 583 

free room. About 3 lb. of this solution is required as the first 
coat on a 50- foot split. A change is made in the second coat, 
in order to keep the oil away from the surface. If the same 
amount of oil were used in the second coat as in the first, the 
goods would dry out sticky, and with very little heat it would 
fry out and the color would be spoiled. The second coat is 
made up with about half the amount of oil as in the first coat. 
As a rule, a 10-oz. cotton is used, to which is added 2 lb. of 
oil, the object being to smooth off the stock with the least 
amount of material. About 2 lb. of this solution is required 
for each 50-foot split. The hide is hung up to dry, and the 
third coat consisting of a 12-oz. cotton, to which 6 oz. of oil 
is added, is applied. When it is desired to produce a better 
grade or a brighter finish a fourth coat is spread on the hide. 
Having applied the necessary number of bottom coats the 
goods are embossed with any design of grain desired. 

To obtain a bright finish, the goods, after embossing, are re- 
coated with a very thin solution of pyroxylin, say about 2 oz. 
to the gallon. Care should be taken that it contains the full 
amount of amyl-acetate or a substitute to keep it from having 
any tendency to become whitish, as even a black color has a 
tendency to show a grayish tinge if this precaution is not ob- 
served. This thin coat is generally applied with a sheepskin 
swab tacked over a board about the size of the brush, say 2\ 
by 6 inches. Bright finishes may also be improved by giving 
a final coat of linseed-oil varnish. 

To make a dull shade, take a solution of pyroxylin, prac- 
tically 2 oz.^ to the gallon, and add 4, 5, or 6 oz. of ground 
pigment to it. To be in proper condition this pigment must 
be ground in some oil medium. For artificial leather, tons 
of pigments are ground in castor oil. There is an objection 
to the use of castor for the top coat, as it does not give as dull 
a finish as it would if the color were added without any oil. 
The material best suited for dull finish is crude birch tar oil. 
It is made from the birch tree, and has somewhat the odor 
of wintergreen oil. It can be purchased in the wholesale 



584 PRACTICAL TANNING 

market at 10 or 12 cents per lb., whereas the refined birch 
oil costs more than that per ounce. 

The crude is perhaps better than the refined oil on account 
of the fact that in grinding it has less tendency to evaporate. 
If not used in too large quantities this also gives a pleasant 
odor to the leather. The amyl-acetate odor for leather is 
rather objectionable, as even the most refined will leave behind 
an amyl or fusel oil odor for a long time, even for years, 
if the goods are not exposed to the air. 



CHAPTER XXI 

ANALYTICAL METHODS* 

Water analysis. — It is quite evident that chemical con- 
trol of the tannery should start with an analysis of the water 
that is to be used in practically every operation which the 
hides undergo while being made into leather. According to 
Procter, the most important determinations are total solids, 
ash, organic matter, sulphates, chlorides, iron, temporary hard- 
ness, permanent hardness, magnesia hardness, free carbonic 
acid, and sodium carbonate. 

As a general statement, the purer the water the better it 
is suited for use in the tannery. It is evident, therefore, that 
the lower the total solids and ash the better for this purpose. 
Organic matter is liable to be accompanied by putrefactive bac- 
teria, the action of which might cause serious damage to the 
hides or skins in all the beam-house operations up to the actual 
tanning process. Sulphates and chlorides to some extent tend 
to prevent the necessary swelling of the heavier leathers in 
the tanning liquors. Also, if present in large quantities, they 
interfere with the extraction of tanning material ; for example, 
water containing a large amount of chlorides has been found 
to cause a considerable loss of tannin in the case of oak bark, 
pine bark, and sumac. Iron would unite with the tannins, 
forming bad stains, and would thus make the water unsuitable 
in all cases except where only black leather is to be made. 
Hardness in general is objectionable, temporary being more so 
than permanent. Temporary hardness slows up the soaking 
process, decreases the efficiency of sodium sulphide solution 
as a depilant, interferes with de-liming due to the formation 
of CaCOs in the hide, and causes loss of tannin in the leach- 
ing and tanning process. Owing probably to its alkalinity, 

*Many of the methods given in this chapter were compiled by Ernest Little while 
instructor in chemistry at Pratt Institute, Brooklyn, N. Y. 

585 



586 PRACTICAL TANNING 

calcium carbonate causes oxidation of the tannin and con- 
sequent darkening of the leather. It will react with the fat- 
liquor, precipitating insoluble calcium and magnesium soaps, 
as well as precipitating some of the aniline dyes. The action 
of temporary hardness in forming boiler scale is well known. 

Permanent hardness is as objectionable in boiler water as 
temporary hardness. It would act the same as the latter in 
the fat-liquors, but will cause a much smaller loss of tannins 
and dyestuffs. Carbonic acid and sodium carbonate would 
cause CaCOs to be precipitated in the hide during the de- 
liming process. Sodium carbonate, like other alkaline salts, 
will cause oxidation of vegetable tanning liquors with a con- 
sequent bad color. 

Total solids. — 100 cc. of sample is evaporated to dry- 
ness in a weighed platinum dish on a water-bath, then dried 
to constant weight at 100° C, cooled in a desiccator, and 
weighed. Increase in weight X 1000 = parts total solids 
per 100,000 parts of water. 

Ash. — The above residue is ignited until the ash is white 
and weight is constant, cooling the dish in desiccator as usual, 
before weighing. Weight of dish -f- ash — weight of dish 
= grams of ash. Grams of ash X 1000 = parts per 
100,000. 

Organic matter. — Moisten the ash in the platinum dish with 
ammonium carbonate solution. This solution is then evap- 
orated to dryness, dried at 100° C, and weighed. This 
weight, subtracted from the weight of the dish -\- total sol- 
ids, gives the weight of organic matter in the sample, then 
grams of organic matter X 1000 = parts per 100,000. 

The ammonium carbonate solution is added in order to cor- 
rect for any carbonates which may have been decomposed by 
overheating. 

Sulphates. — 250 cc. of filtered sample is acidified with 2 
cc. of concentrated hydrochloric acid. The solution is heated 
to boiling, and 15 cc. of 10 per cent barium chloride solution 
is added very slowly with constant stirring. Boil the solution 






ANALYTICAL METHODS 587 

gently for 10 minutes, allow the solution to stand about 30 
minutes, filter, wash thoroughly with hot distilled water, ig- 
nite, and weigh. Weight of BaS0 4 X 0.342X400 = parts 
of S0 3 per 100,000. 

Chlorides. — 100 cc. of sample is placed in a small porcelain 
casserole and 2 drops of potassium chromate solution ( free 
from chlorides) added. Run in N/10 silver nitrate solution 
(4.25 grams AgNC>3 per 250 cc.) from a burette until one 
drop causes a permanent red-brown tinge in the solution, then, 
cc. N/10 AgNO s solution used X 0.00355 X 1000 = parts 
of chlorine per 100,000. 

Iron. — 500 cc. of sample is made acid with sulphuric acid, 
and evaporated to dryness in a porcelain casserole. Add a 
few drops of concentrated nitric acid and ignite gently until 
all organic matter is destroyed. Warm the residue with 15 cc. 
distilled water and 5 cc. 1 : 1 HC1, and wash the filter-paper 
thoroughly. Add dilute potassium permanganate solution 
drop by drop until slight pink color remains 5 minutes. Avoid 
adding too much dilute potassium permanganate solution. To 
this colorless solution add 10 cc. of 2 per cent potassium 
sulphocyanide, put in Nessler tube and dilute to 100 cc. and 
stir thoroughly. Into a second Nessler tube add 15 cc. of 
distilled water,, 5 cc. 1 : 1 hydrochloric acid, then treat with 
dilute potassium permanganate and potassium sulphocyanide 
exactly as above, dilute to a little less than 100 cc. (about 99.5 
cc.) and add standard iron solution drop by drop until in the 
well-mixed solution is the same depth of color as in the first 
tube. 

The iron solution is made by dissolving 0.1 gram of pure 
iron wire in a little dilute hydrochloric acid, to which a few 
drops of concentrated nitric acid have been added. This so- 
lution is then diluted to 1000 cc, and 1 cc. of solution = 
0.0001 gram of iron. 

Temporary hardness. — 200 cc. of sample is titrated with 
N/10 acid until faint pink color appears, using methyl-orange 
as an indicator. 1 cc. N/10 acid = 0.005 gram CaCO.3 ; re- 
port parts per 100,000. N/50 acid will give a better titration. 



688 PRACTICAL TANNING 

1 cc. N/50 acid = 0.001 gram CaCOs- If N/50 acid is 
used, 100 cc. of sample should be titrated. 

(Note: If alkaline hardness is present, the amount of N/10 
acid necessary to neutralize it should be subtracted from the 
above volume of N/10 acid before temporary hardness is 
calculated.) 

Permanent hardness. — Measure 200 cc. of sample into a 
porcelain casserole, boil to expel CO2, add 25 cc. of N/10 
sodium hydroxide, and evaporate to about 50 cc. Cool, filter, 
wash the filter-paper thoroughly, dilute the filtrate to about 
100 cc, add a few drops of methyl-orange, titrate to faint 
pink, point with N/10 acid. 

The number of cubic centimeters of N/10 acid used, sub- 
tracted from 25 = cc. of N/10 acid, corresponding to perma- 
nent hardness in 200 cc. of water. 

1 cc. of N/10 acid = 0.005 gram CaCOs- Report perma- 
nent hardness as parts of CaCOs per 100,000. 

Magnesia hardness. — This is calculated as follows : remove 
temporary hardness from 100 cc. sample with N/10 acid, as 
described above. Boil to about 85 cc. to expel all CO2. 
Transfer to 200 cc. glass-stoppered graduated flask; add 100 
cc. of lime water, the value of which is known in terms of 
N/10 acid. Heat nearly to boiling; cool, and make up to 
mark with boiled distilled water. Pipette off 100 cc. of clear 
supernatant liquid, and titrate with N/10 acid, using phenolph- 
thalein as an indicator; then cc. of N/10 acid necessary to 
neutralize 50 cc. lime water — cc. N/10 acid used in final ti- 
tration = cc. N/10 acid corresponding to magnesia hardness 
in 50 cc. sample. 1 cc. N/10 acid = 0.005 gram MgC0 3 . 
Report magnesia hardness as parts of MgCOs per 100,000. 

Free carbonic acid. — 100 cc. sample are titrated with N/10 
sodium carbonate, using phenolphthalein as indicator. When 
all of the carbonic acid has been converted to NaHCOs by 
the Na2COs, and there is slightest excess of Na2COs, the 
solution will turn pink. 

Alkaline carbonates. — In the determination of permanent 



ANALYTICAL METHODS 589 

hardness, if the alkali found by the final titration is in excess 
of the alkali added, this excess is due to alkaline carbonates, 
and should be calculated as Na2COs. 

Cc. N/10 acid used in titration — cc. N/10 alkali added = 
cc. N/10 corresponding to alkaline carbonates in 200 cc. of 
sample. 1 cc. N/10 acid = 0.0053 gram Na 2 C0 3 . Report 
alkaline carbonates as parts of Na2CO.s per 100,000. 

Soaks. — The only determination of any importance in the 
analysis of soak water is that of hide substance, this being a 
measure of the extent to which the hides are being decom- 
posed. 

Stiasny's method. — 200 cc. of soak water is poured into 
a 250 cc. graduated flask; 20 cc. of a 5 per cent solution of 
zinc sulphate is now added, and the solution made up to the 
mark. Allow the solution to stand 5 minutes and filter 
through a 15 cc. pleated filter. Titrate 50 cc. of filtrate, as 
a blank, against N/10 sodium hydroxide, using phenolphtha- 
lein as an indicator. To another 50 cc. portion add 10 cc. of 
40 per cent formaldehyde, which has been treated with pure 
barium carbonate, and titrate as above. The difference in the 
two burette readings is due to the amino acids which are 
formed by the decomposition of the hide substance. These 
acids condense with the formaldehyde, forming methylen- 
amino acids, which give a good titration and a sharp end-point 
when phenolphthalein is used as an indicator. 

cc.N/lONaOHX 0.00786X25X3.785 J pounds of hide substance 
453.6 P er gallon 

or 

cc. N/10 NaOHX 0.00164 = pounds of hide substance per gallon. 

The hide substance in soak water can be more accurately 
determined by the Kjeldahl method, but the above procedure 
is much quicker and more satisfactory for control. 

Lime. — The most important determination in the analysis 
of lime is that of available lime. The determination of iron, 
calcium, magnesium, and alkalinity of a saturated solution 
may also be of great importance in individual cases. As a 



590 PRACTICAL TANNING 

general statement, a good lime should -contain about 90 to 
95 per cent available CaO. The presence of MgO in quan- 
tities greater than 2 per cent is objectionable, owing to the 
fact that improper slaking may result and the hides may be 
burned by the small lumps of CaO. The objections to iron 
in any but small traces are well known. 

Available lime. — Weigh 1 gram of a uniform sample and 
transfer it to a 1 -liter graduated flask. The flask is then filled 
to the mark with well-boiled hot water. The flask is stop- 
pered at once and shaken frequently during the next few 
hours to ensure complete solution of the lime. When the 
solution is cold, it is again made up to the mark, shaken, and 
allowed to settle; then 50 cc. of the clear liquid is pipetted 
off and titrated with N/10 hydrochloric acid, using phenolph- 
thalein as an indicator. 

cc.N/l OHCl X 20 X 0-0028 X 100 _ M K1 n n 

weight ot sample 

Iron, calcium, and magnesium. — A 5-gram sample is 
weighed into a porcelain dish, and 25 cc. of concentrated hy- 
drochloric acid is added. Cover dish with a watch-glass and 
boil until solution is complete. Rinse off the watch-glass and 
evaporate to dryness on the water-bath. The residue is treated 
with dilute hydrochloric acid and filtered into a 250 cc. grad- 
uated flask. Wash the filter-paper thoroughly. Cool the fil- 
trate, make up to mark and mix well ; 25 cc. of this solution 
are taken and Fe, Ca, and Mg are determined by the usual 
analysis. The Fe being precipitated by NH4CI -f- NH4OH 
in hot solution, the calcium is precipitated as CaC^C^ in a 
weak NH4OH solution ; and magnesium is precipitated as 
MgNH4P04 in a faintly ammoniacal solution, then one-third 
of its volume of concentrated NH4OH is added, and the solu- 
tion is allowed to stand over night before filtering. Re-pre- 
cipitation is necessary in each operation. 

The iron can also be determined by taking 25 cc. of the 
above solution, making acid with nitric acid, boiling a few 
minutes, and transferring to a 100 cc. graduated flask; make 



ANALYTICAL METHODS 591 

up to mark and determine iron colorimetrically with potas- 
sium sulphocyanide as outlined under water analysis. 

Alkalinity of saturated solution. — This determination is of 
importance owing to the fact that an impure lime may possibly 
show greater alkalinity than a pure one, as the impurities may 
react with the lime to form more soluble bases than Ca(OH)2. 

One gram of lime is shaken thoroughly with 100 cc. of 
water, and the method proceeded with as in the determination 
of available lime. [50 cc. of a saturated solution of pure lime 
at room temperature (15° C.) will neutralize 23.6 cc. of 
N/10 HO.] If more hydrochloric acid than this is required 
it will be for the reasons given above. 

Sodium sulphide. — Commercial sodium sulphide is usu- 
ally obtained either in the crystalline form or fused. The 
first form has the formula Na2S.9HoO, and contains about 
32.5 per cent Na2S; the other salt contains less water and 
about 60 per cent NasS. The most common impurities of so- 
dium sulphide are Na 2 C0 3j Na 2 S0 4 , Na 2 S20 3 , NaOH, and 
polysulphides. 

The percentage of Na2S.9H20 (or sulphide sulphur) and 
the NaOH in the sodium sulphide are the determinations usu- 
ally made. 

Na^S.^H-jO. — Twelve grams of the sample is dissolved 
in water and made up to 1000 cc ; 10 cc. of this solution are 
pipetted into a 200 cc. beaker, diluted to about 100 cc, and 
titrated at once with an N/10 zinc sulphate solution until one 
drop gives no dark turbidity with nickel sulphate (or purple 
color with sodium nitro-prusside) used as an outside indicator. 

The zinc sulphate solution is made by dissolving 3.27 grams 
of c.p. zinc in dilute hydrochloric acid (the zinc being in con- 
tact with a piece of clean platinum), then adding an excess of 
ammonium hydroxide, 50 grams of ammonium chloride, and 
making up to one liter. Or, dissolve 14.35 grams of pure 
ZnS0 4 .7H 2 in water, add NH 4 OH until the precipitated 
Zn(OH) 2 re-dissolves, add 50 grams of NH4CI, and make up 
to one liter. 



592 PRACTICAL TANNING 

cxt nnirn cc.N /10 Z11SO4 sol. X 100X0.012 X 100 

Percentage of Na2b.9-H.2U = —cr — 7- — ■ — i ; 

& weight of sample 

or 

£ >T cc.N /IOZ11SO4 sol. X 100X0.0039X100 

Percentage of N a 2 b = ^rr — 2 — ~n 

& weight of sample 

Polysulphides, sulphates, or thiosulphate are not included in 
this determination, only those sulphides which would yield 
hydrogen sulphide and hydrochloric acid. 

Total alkalinity and NaOH in the Na?,S. — Pipette 50 cc. 
of the above solution into a 200 cc. beaker, dilute to 100 cc, 
and titrate with N/10 hydrochloric acid, using- methyl-orange 
as an indicator. This gives total alkalinity. The sodium hy- 
droxide in the Na2S.9H20 can be calculated as follows: 

Percentage of NaOH = 

cc. N/10HC1— 5(cc. N /10ZnSO 4 sol.) X 20X0.004 
weight of sample 

When Na2S is dissolved in water it is hydrolyzed consid- 
erably into NaOH + NaSH, as shown in the equation 

Na 2 S+H 2 = NaOH+NaSH 

Both of these products of hydrolysis, as well as the non- 
hydrolyzed Na 2 S, react with the N/10 HC1. 

(1) NaOH+HCl = NaCl + H 2 

(2) NaSH + HC1 = NaCl + H 2 S 

(3) Na 2 S + 2HC1 = 2NaCl+H 2 S 

Any free NaOH originally present in the sample will also 
react according to equation ( 1 ) . Therefore the number of 
cubic centimeters of N/10 hydrochloric acid used in this tritra- 
tion were used in reacting with Na2S, NaSH, and NaOH 
formed by hydrolysis and NaOH originally present as such. 
Therefore the cc. of N/10 zinc sulphate solution necessary, 
subtracted from cc. of N/10 HC1 for the same size sample, 
gives the cc. of N/10 HC1 necessary to neutralize the free 
NaOH. This may be clearer if we look at the problem in 
this way: The number of cc. of N/10 zinc sulphate solution 
is the same as it would have been had there been no hydrol- 



ANALYTICAL METHODS 593 

ysis. This number of cc. of N/10 zinc sulphate solution is 
exactly equal to the number of cc. of N/10 acid necessary to 
react with NaoS, NaSH, and NaOH formed by hydrolysis. 
Therefore, the cc. of N/10 zinc sulphate solution subtracted 
from the cc. of N/10 acid used in the determination of total 
alkalinity gives the cc. of N/10 acid necessary to neutralize 
the free NaOH. • Methyl-orange is not sensitive to H2S, so 
it does not interfere with the titration. 

Analysis of arsenic sulphide. — Red arsenic is composed 
chiefly of AS2S2, with some AS2S3, and containing AS2O3 
and free sulphur as impurities. These substances are use- 
less as depilating agents, only sulphide sulphur being 
available for this purpose. For a complete analysis, deter- 
mine the percentage of arsenic and the amount of soluble sul- 
phides produced by the action of sodium hydroxide on the 
sample. 

Arsenic. — 5 grams of the powdered sample are weighed in 
a beaker and boiled with concentrated nitric acid, covering 
the beaker with a watch glass. This nitric acid treatment 
dissolves the arsenic and oxidizes it to H3ASO4. When solu- 
tion is complete, evaporate off most of the acid on the water- 
bath, dilute, and filter. To the filtrate add an excess of am- 
monium hydroxide and about 20 cc. of clear magnesia mixture. 
Allow it to stand 24 hours, filter, and wash with 3 per cent 
ammonia water. Dry the MgNFLiAsC^ and separate from 
the filter-paper. The paper is ignited in a weighed porcelain 
(not platinum) crucible. The precipitate is then added to 
the same crucible and the whole gradually heated to a red 
heat, which is maintained for 10 minutes. The Mg2As207 
in the crucible is now weighed, and the weight of the empty 
crucible subtracted. 

, . „ grams Mg 2 As 2 7 X 0.6985X100 

Percentage of As 2 S 2 = r-7— — 7 i 

fe weight of sample 

Sulphide sulphur (Procter's method.) — One gram of the 
sample is digested for 3 hours with 50 cc. of 10 per cent so- 
dium hydroxide solution, with frequent shaking. Make up 



594 PRACTICAL TANNING 

to 100 cc. with distilled water and filter; 50 cc. of the filtrate 
is titrated with N/10 zinc sulphate solution as described under 
analysis for sodium sulphide. 

Percentage of active sulphur = 

cc. N /10 ZnS0 4 sol. X2 X0.0016 X 100 

or 

Percentage of active sulphur = cc. N/10 ZnS0 4 sol.X0.32 

Lime liquors. — The most important determination in the 
analysis of limes is that of hide substance. Too high a hide 
substance content indicates putrid limes and loss of stock. 
Soluble lime, available lime, and CaC03 are also factors that 
are sometimes useful. 

Soluble lime and hide substance. — The sample of lime liq- 
uor (which has been collected after thorough plunging of the 
limes) is well shaken and carefully mixed. About 100 cc. of 
this liquor is filtered at once through a dry filter-paper into a 
clean, dry beaker; 50 cc. of this filtrate is pipetted into a 500 
cc. graduated flask and diluted to the mark with water free 
from CO2. Difficulty is often experienced in filtering this 
lime liquor. Colloidal hide substance will fill up the pores of 
the filter-paper and make filtration a very slow process. Also 
finely divided particles of lime sometimes pass through the 
filter-paper, giving a cloudy filtrate. Under these conditions 
it is better to allow the lime liquor to stand over night in a 
stoppered bottle, then filter the clearer upper portion of the 
lime liquor through a dry paper. This filtrate is well mixed, 
100 cc. are pipetted off and titrated with N/10 acid, using 
phenolphthalein as an indicator. When the phenolphthalein 
end-point has been reached, add a couple drops of methyl- 
orange and then add N/10 hydrochloric acid, drop by drop, 
until solution turns pink. 

Percentage of soluble Ca(OH) 2 = 

cc. N/10 phenolphthaleinX0.0037XlOO 
10 

The amount of acid used after reaching the phenolphtha- 
lein end-point until the methyl-orange end-point is reached 



ANALYTICAL METHODS 595 

is a rough measure of the hide substance present. This is 
due to the fact that the calcium salts of many of the prod- 
ucts of decomposition of hide substance, as albuminates, and 
amino acids, do not change methyl-orange, although they do 
destroy the pink color of the salt of phenolphthalein. Ap- 
proximately 0.0053 gram of hide substance when in solution 
would in this way furnish enough alkalinity to neutralize 1 
cc. of N/10 acid; therefore, 

cc N /10 HC1 (m.o.) X 0. 0053X100 
Percentage of hide substance = 7q 

Ten cubic centimeters of a saturated solution of pure Ca 
(OH) 2 will neutralize 4.72 cc. of N/10 HC1. If more than 
this amount of HC1 is used in the above titration (phen- 
olphthalein -f- methyl-orange together) the reason is the pres- 
ence of NH 3 resulting from the decomposition of the hide 
or to added salts reacting with the lime to form other alkalies. 

Two other more accurate methods of determining hide sub- 
stance in lime liquors are taken up later. 

Available lime and CaCOz- — Available lime constitutes the 
dissolved lime and the lime not in solution ; CaCO.3 is usually 
present in small amount and is not of great importance of 
itself, but it must be considered in order to get an accurate 
determination of available lime. 

The sample is thoroughly mixed, and 10 cc. of unfiltered 
liquor are pipetted out, washed into a liter flask with water 
free from CO2, and diluted to the mark; 100 cc. of this 
solution (1 cc. of original lime liquor) are measured into a 
200 cc. beaker and titrated with N/10 HC1, using first phe- 
nolphthalein and then completing the titration with methyl- 
orange as an indicator. 

(a) cc. N/10 HC1 used for the phenolphthalein titration 
were used in neutralizing all the available Ca(OH)2 + 
^CaCO.3 present. 

(b) cc. N/10 HC1 used for the methyl-orange titration 
were used in neutralizing ^CaCC>3 + hide substance. 

(c) Therefore from (b) we get cc. of N/10 HC1 necessary 



596 PRACTICAL TANNING 

to neutralize |CaC03 = cc. of N/10 HC1 used in above 
methyl-orange titration, — 1/10 the number of cc. of N/10 
HC1 found necessary to react with the hide substance in the 
above determination of soluble lime and hide substance. 

Therefore : 

Percentage of CaC0 3 = 

2Xcc. N/10 HC1 for \ CaCOsX 0.005X100 

From (a) we get — cc. N/10 HC1 to neutralize available 
Ca(OH)o=cc. N/10 HC1 used in the above phenolphthalein 
titration — cc. N/10 HC1 necessary to neutralize \ CaCOs- 
[This was found in (c).] 

Therefore the percentage of available Ca(OH)2=cc. N/10 
HC1 used in the above determination — cc. N/10 HC1 neces- 
sary to neutralize ICaCOs [found in (c)] X 0.0037 X 100. 

Hide substance continued. — The following approximate 
method may be of some use for control work. The chem- 
istry involved is that the amino acids do not affect phenol- 
phthalein, but when treated with formaldehyde they are con- 
verted into more strongly acidic compounds which can be 
titrated with N/10 NaOH, using phenolphthalein as an 
indicator. 

Twenty-five cubic centimeters of filtered lime liquor is just 
neutralized with N/10 acid and a faint pink color (using 
phenolphthalein as an indicator) produced with a couple of 
drops of N/10 NaOH; 10 cc. of 40 per cent formaldehyde 
(neutral to phenolphthalein) is now added, and the solution 
titrated with N/10 sodium hydroxide. 

No accurate factor is known to convert this reading into 
hide substance, but the cc. of N/10 acid used may be of value 
in comparing the relative amounts of the products of decom- 
position of hide substance in different limes. 

Kjeldahl method for hide substance. — Filter a sample of 
the lime liquor to remove hairs or other suspended particles 
containing nitrogen. Pipette about 150 cc. of this filtrate 
into a Kjeldahl flask, and boil gently until the volume is re- 
duced to a few cubic centimeters. Thirty cubic centimeters 



ANALYTICAL METHODS 597 

of concentrated sulphuric acid and 15 grams of potassium 
sulphate, together with about three glass beads are now added 
and the solution, heated gently at first, is then boiled until all 
organic matter is destroyed and the solution is colorless. Cool 
and pour slowly with stirring into 100 cc. cold water. Trans- 
fer this to a 200 cc. graduated flask, rinsing out the beaker 
thoroughly and make up to mark with distilled water. Pipette 
out 50 cc, transfer to Kjeldahl flask, dilute to 100 cc. and 
make the solution strongly alkaline with a saturated solution 
of sodium hydroxide. Connect to a straight condenser by 
means of a Hopkins distilling head, and distill for about an 
hour. The distillate is caught in an Erlenmeyer flask con- 
taining 50 cc. of N/10 HC1 + 2 drops methyl-orange. The 
end of the delivery tube extends below the surface of the acid. 
After about 75 to 100 cc. have distilled over, distillation is 
stopped, and the condenser and delivery tube are carefully 
rinsed with distilled water. The acid is now titrated with 
N/10 NaOH in order to determine the amount of acid not 
neutralized by the ammonia. 

1 cc. N/10 acid = 0.0014 gram of nitrogen or 0.00786 
gram of hide substance; 5.62 grams of dry hide substance = 
1 gram of nitrogen. 

cc. N /10 acid X 0.00786 X 100 
Percentage of hide substance = 275 

or 

Percentage of hide substance = cc. N/10 acid X 0.02096 

Sulphide lime liquors: Sodium sulphide. — 50 cc. of fil- 
tered liquor is pipetted off, diluted to about 150 cc, and 
titrated with N/10 zinc sulphate solution as described under 
analysis of sodium sulphide. 

_ cc. N /10 ZnS0 4 sol. X 0.0039 X 100 ■ 
Percentage of Na 2 S = ■ ^0 

or 

cc.N/10 ZnSQ 4 sol.X 0-012 X 100 
Percentage of Na 2 S. 9H2O— jj-q 



\ 



598 PRACTICAL TANNING 

The following is a good method, but is much longer than 
the method given above. The sample is filtered, and 25 cc. 
of the filtrate is pipetted into a 200 cc. beaker; 25 cc. of 
5 per cent cadmium chloride and 15 cc. of acetic acid are 
added, and the solution is boiled and filtered. Wash the 
precipitate with hot water, dissolve in dilute hydrochloric 
acid, and titrate with N/10 iodine solution using starch as 
an indicator. 

, >T _ cc. N /10 iodine X 0.0039 X 100 
Percentage of Na 2 S = ^ 

or 

r at o nu n CC - N / 10 iodine X 0012 X 10 ° 

Percentage of Na 2 S. 9H 2 = ^ 

Soluble lime and hide substance. — The analysis is carried 
out exactly as that indicated under lime liquor. In this case 
the phenolphthalein end-point gives not only the dissolved 
alkalies, but also half of the Na2S due to its hydrolysis: 
Na 2 S + H 2 = NaOH + NaHS. 

Percentage of soluble Ca(OH) 2 = 

cc. N/10 HC1— V 2 cc. N/10 ZnSQ 4 sol. X 0.0037 X 100 

10 

The cc. of N/10 acid used after reaching phenolphthalein 
end-point to the methyl-orange end-point are used in neutral- 
izing the calcium salts of the decomposition products of the 
hide (so-called dissolved hide substance) -f- half of the Na 2 S 
present. 

Percentage of hide substance = 

cc. N /10 HClQn.o.)— 1 / 2 cc. N /10 ZnSQ 4 sol. X 0.0053 X 100 

10 

The above method for hide substance determination is only 
approximate and should not be relied on when the Kjeldahl 
method can be made. The latter method is run exactly as 
outlined under lime liquors, and is much more dependable. 

In running the formaldehyde method for hide substance, 
the sulphides must first be oxidized to S, otherwise they will 



ANALYTICAL METHODS 599 

react with the formaldehyde, forming compounds which 
greatly increase the alkalinity of the solution. The method 
as outlined by Stiasny is given below : 

The liquor is filtered, 50 cc. pipetted into a beaker, diluted 
to 150 cc, and two drops of phenolphthalein added. Make 
slightly acid with acetic acid, and add N/10 iodine in slight 
excess. Titrate with N/10 NaOH until the solution becomes 
pink, then add 10 cc. of neutral 40 per cent HCHO ; add 
N/10 NaOH until the phenolphthalein end-point appears. 
The cc. of N/TO NaOH used in this last titration is a measure 
of the amino acids in solution. 

Available lime and CaCOz. — The method can be run ex- 
actly as outlined under lime liquors. Here the phenolphtha- 
lein end-point will give available Ca(OH)2 -f- 4CaCO:-, 
+ -i-Na2S. Therefore, subtract from the total number of 
cc. of N/10 acid used, half the number of cc. of N/10 zinc 
sulphate solution used for the same size sample, and proceed 
with the calculation of available lime as outlined under lime 
liquors. 

The cc. of N/10 HC1 used after reaching the phenolphtha- 
lein end-point until the methyl-orange end-point is reached 
are used up in neutralizing ^CaCOs -f- hide substance -f- 
-}Na2S. Therefore, subtract from the total number of cc 
of N/10 acid used, half the number of cc. of N/10 zinc sul- 
phate solution used for the same size sample, and proceed with 
the calculations of CaCOs as outlined under lime liquors. 

De-liming test. — In de-liming limed hides and skins by 
means of acids it is customary to determine the completion 
of the process by applying a solution of phenolphthalein to a 
freshly cut section of the pelt. If such a solution is applied 
to a limed pelt, the section shows red; if to a completely 
de-limed pelt, there is no change of color. A partly de-limed 
pelt will show red in the middle and colorless on either side. 
Most tanners usually allow the de-liming to proceed to a given 
point. For some purposes complete de-liming is necessary, 
while for others a mere surface de-liming is sufficient, the 



600 PRACTICAL TANNING 

depth depending upon the nature of the subsequent tanning 
process. For example, if it is a question of sheepskins which 
are first de-limed with acid, then bated or puered, the first 
actual acid de-liming is usually carried out only to such an 
extent that a streak of free lime is left in the middle. With 
heavier goods, such as sole leather, the extent of the acid 
de-liming depends upon the nature of the liquors into which 
the goods are next placed. If the tail suspension liquors are 
very acid in character, it is not as important to neutralize 
as much lime as if these liquors were only slightly acid. The 
phenolphthalein test can be applied with almost any acid, but 
there is one caution that might be mentioned in its use, and 
that is that its action is more qualitative than quantitative. 
A trace of lime will give as strong a coloration as a large quan- 
tity of free lime, and cases have been known where this has 
led to confusion. To make the matter clear, it may be well 
to take a definite example : 

Suppose that fully limed sole butts are being de-limed with 
one of the ordinary acids, and that the amount of acid present 
in the liquor is not quite sufficient to neutralize the whole of 
the lime; at the beginning of the process the whole section 
will show red on application of phenolphthalein, and after a 
short time the cut section will show red in the middle and 
colorless at the outsides. The depth of the outside strips will 
increase as the process goes on, until almost the whole of the 
acid has been neutralized by the free lime in the hides. When 
this point has been reached there will be a minimum red sec- 
tion in the center, but afterwards the free lime in the center 
will gradually diffuse out to the extremities, and so, on applica- 
tion of phenolphthalein, the whole section will show red. In 
this way it is possible for an almost completely de-limed hide 
to appear as though it were not de-limed at all. It is in this 
sense that the test is qualitative rather than quantitative. By 
taking cut sections at different stages of the process, and not 
only at the end, it is possible to determine exactly the actual 
extent of the de-liming. 

Salt. — For moisture determination dry 5 grams of the sam- 



ANALYTICAL METHODS 601 

i 

pie in a tared dish at 100° C, over night. Weigh the loss in 
weight as water. 

Calcium oxide (CaO). — Pipette 50 cc. of a solution made 
from 25 grams of the sample in 250 cc. water, into a 250 cc. 
beaker, make alkaline with ammonia, and bring to a boil on 
hot plate. Add an excess of ammonium oxalate and digest 
the solution for a half -hour. Filter the precipitate, and wash 
free from chlorides. Ignite, blast, cool, and weigh quickly 
as CaO. 

Sulphates (SO3). — Dilute 50 cc. of the above solution to 
about 100 cc, acidify with HC1, bring to a boil on a hot plate, 
and precipitate the sulphates with barium chloride. Digest for 
a half-hour, filter, and wash free from chlorides. Ignite, 
cool and weigh as BaSCU. Calculate to SO3. Test for traces 
of iron and magnesium. The NaCl is found by difference. 

Aluminum sulphate. — Weigh out 6 grams of the pulver- 
ized sample, dissolve in water, and dilute to 250 cc. 

Aluminum oxide (AI2O3). — Pipette 25 cc. of the above 
solution into a 250 cc. beaker, add 2 cc. of concentrated hydro- 
chloric acid, dilute to about 100 cc, and bring to boil. Pre- 
cipitate the aluminum from the boiling solution with a slight 
excess of ammonia. Boil until the solution smells but faintly 
of ammonia, filter, wash the precipitate, and ignite. Blast 
the precipitate, cool, and weigh, and repeat until the weight 
is constant. Calculate as AI2O3. 

(Note: — If iron is present in the sample, the amount found 
under Fe203 must be subtracted from the precipitate.) 

Total sulphuric acid (H2SO4). — Pipette 25 cc. of above 
solution into a porcelain casserole, dilute with about 150 cc. 
of water, and add a little phenolphthalein. Run in N/10 
NaOH till the pink color remains on stirring. Heat and boil 
for one minute. Run in more N/10 NaOH and repeat the 
boiling, finally titrating to the end-point. This determination 
gives the sulphuric acid combined with the aluminum and any 
free acid present. 

Free sulphuric acid (H2SO4). — From the two above de- 
terminations, the sulphuric acid necessary to form the normal 



602 PRACTICAL TANNING 

salt may be calculated. Formula: Al2(S04)3-18H20. Any 
excess of acid is figured as free sulphuric acid. 

Ferric oxide (Fe 2 Os). — The sample should be tested for 
iron with potassium sulphocyanide. If present, proceed as 
follows: Weigh 25 to 50 grams, according to the amount 
of iron present, into a large Jena flask. Dissolve in about 
500 cc. of water and make strongly acid with sulphuric acid. 
Add 5 grams of powdered zinc and heat on the steam bath 
till the action ceases, then test for ferric iron with 
K 4 Fe(CN)6. If the zinc contains iron, a blank must be run. 
Remove the flask from the bath if the iron is reduced, 
filter quickly, cool, and titrate with standard potassium 
permanganate. 

Pickle. — The reagents are as follows : 

Sodium hydroxide: N/10 solution, 1 cc. = 0.0049 gram 

H 2 S0 4 . 

Silver nitrate : 2.9 grams per liter, 1 cc. = 0.001 gram NaCl. 

Phenolphthalein : 1 gram per 100 cc. of alcohol. 

Potassium chromate : 1 gram per 100 cc. of water. 

Sulphuric acid. — Pipette 10 cc. of pickle into a 250 cc. 
casserole, to which add 100 cc. of water and 3 drops of phen- 
olphthalein. Run in standard NaOH solution from burette 
with constant stirring until the liquid shows a faint pink color. 

cc. N/10 NaOH X 0.0049 X 10 = x; x = grams of 
H2SO4 per 100 cc, 

Jo^^L orx X 0.0835 = y;y = pounds of H 2 S0 4 per gallon. 
453.6 X 100 

pounds of commercial H2SO4 per gallon. 



0.935 

(Note: — 3785 cc. = 1 gallon; 453.6 grams in 1 pound.) 
Sodium chloride. — Dilute 10 cc. of pickle with water to 
500 cc. in a 100 cc. graduated flask. Shake well and pipette 
10 cc. into a 250 cc. casserole, then neutralize the acidity by 
a very slight excess of pure calcium carbonate. Then add 
five drops of potassium chromate solution and run in silver 
nitrate from burette, with constant stirring until the yellow- 
ish-white color changes to a slight reddish-brown. 



ANALYTICAL METHODS 603 

cc. AgNOs X 0.001 X 500 =x; x = grams of NaCl per 
100 cc. 

x X 3785 or x X 0.835 = pounds of NaCl per gallon. 
453.6 X 100 

Some standard of concentration should be adopted in the 
preparation of pickle and 1 lb. of salt per gallon of water 
is a convenient strength. The ratio of sulphuric acid to so- 
dium chloride should be 1:8; there should be therefore $ lb. 
or 2 oz. of sulphuric acid per gallon of pickle. 

Formaldehyde: Romijn's method. — 25 cc. of the dry 
formaldehyde solution is weighed accurately in a tared weigh- 
ing bottle with a well-ground stopper, and washed without loss 
into a 500 cc. flask. The solution is made up to the mark, and 
5 cc. is accurately measured into a bottle with a well-ground 
stopper; 30 cc. of N/1 NaOH, which need only be measured 
in a graduated cylinder, is added rapidly. About 50 cc. of 
N/5 iodine is immediately run in from a burette, with fre- 
quent shaking, until the liquid is deep yellow. The bottle is 
stoppered, well shaken for a half a minute, and the contents 
acidified with 40 cc. of N/1 sulphuric acid (measured in a 
graduated cylinder), and after a short time, during which the 
bottle is kept stoppered, the excess of iodine is titrated with 
N/10 sodium thiosulphate. 

HCHO + I 2 + 2H 2 = HCOOH + 2HI. 

Each cc. of N/5 iodine equals 0.003 grams of HCHO. 

Two-bath chrome liquors: Determination of Cr as 
Cr*Oz, NaiCriOi, or NaiCrO^. — 10 cc. of the liquor is placed 
in a 250 cc. graduated flask and diluted to the mark. After 
thorough mixing, 50 cc. is pipetted off and run into a 500 cc. 
beaker; 5 cc. of concentrated hydrochloric acid and 10 cc. of 
10 per cent potassium iodine solution is now added. The 
solution is cooled, diluted to about 400 cc, allowed to stand 
a few minutes, and the liberated iodine titrated with N/10 
Na2S2C>3 solution, using starch as an indicator. Do not add 



604. PRACTICAL TANNING 

the starch until the brown color of the iodine is nearly 
destroyed. 

1 cc. of N/10 Na 2 S 2 3 equals 0.00333 gram Cr0 3 , or 
0.00436 gram Na 2 Cr 2 7 , or 0.0054 gram Na 2 Cr0 4 . 

Grams of CrO s per 100 cc. = cc. N/10 Na 2 S 2 3 X 0.0033 
X50. 

Acidity. — Take 10 cc. of liquor, dilute to 200 cc, and 
titrate with N/10 NaOH, using phenolphthalein as an indi- 
cator. The sodium hydroxide will be taken up by the 
Na 2 Cr 2 07, the H 2 Cr 2 OT, and the free acid as HC1 or H 2 SC>4. 

(262) 

(a) Assume bath is all A/a 2 O 2 07. — Na 2 Cr 2 OT +6KI -f- 

(762) 
14HC1 = 2NaCl + 2CrCl 3 + 6KC1 + 7H 2 + 3I 2 . 

262 : 762 :: 1 : x; x = 2.908 grams of I liberated by 1 gram 

of Na 2 Cr 2 07. 1 cc. N/10 iodine solution contains 0.0127 gram. 

2 908 
Iodine. ' = 228.9 cc. N/10 I solution could be formed 

from the iodine liberated by 1 gram of Na 2 Cr 2 7 . Therefore, 
228.9 cc. N/10 Na 2 S 2 3 will be required to absorb the iodine 
liberated by 1 gram of Na 2 Cr2.07. 

(262) (80) 

Na 2 Cr 2 7 + 2NaOH = 2Na 2 Cr0 4 + H 2 0. 

262 : 80 :: 1 : x; x = 0.3053 grams of NaOH necessary 
to react with 1 gram of Na 2 Cr 2 07. 

1 cc. N/10 NaOH = 0.004 gram of NaOH. 

Therefore, ( j^jj| = 76.3 cc. N/10 NaOH for 1 gram Na 2 Cr 2 7 . 

228 Q 

%^ = 3. When the bath is all Na 2 Cr 2 7 the cc. of N/10 NaOH 
76.3 

= 1/3 cc. N/10 Na 2 S 2 3 . 

Strength = cc. N/10 Na 2 S 2 3 X 0.00436 X 50 = grams 
Na 2 Cr 2 7 per 100 cc. 

(Note: 0.00436 = grams Na 2 Cr 2 7 in 1 cc. N/10 solu- 
tion. 262 (mol. wt.) Na^Cr 2 07 -f- 6 = 43.6 grams of 
Na 2 Cr 2 07 in 1 liter of normal solution.) 



ANALYTICAL METHODS 605 

(b) Assume bath is a mixture of NaiCrzOq and Na^CrO^. 
— Na2Cr04 does not react with NaOH; therefore the cc. of 
N/10 NaOH = a cc . N/10 Na 2 S 2 3 . 

Strength. — cc. N/10 NaOH X 0.0131 X 10 grams 
Na 2 Cr 2 7 in 100 cc. bath. 

(262) 

Na 2 Cr 2 7 grams Na 2 Cr 2 7 in 100 cc _ . , 

— ~-^ = ■ — ; x = grams Cr in form 

— ' \yc x 

(104) 
of Na 2 Cr 2 7 in 100 cc. of bath. 

cc. N/10 Na 2 S 2 3 X 0.00173 X 50 = x or total grains 
Cr in 100 cc. of bath. 

x' — x = grams of chromium as Na 2 Cr04 in 100 cc. of bath. 

(Note: 0.0131 = grams Na 2 Cr 2 7 in 1 cc. N/10 solu- 
tion when Na 2 Cr 2 07 is acting as an acid to neutralize NaOH.) 

262 (mol. wt.) Na 2 Cr 2 7 -5- 2 = 131 grams Na 2 Cr 2 7 
for 1 liter of normal solution; 0.00173 = grams Cr in 1 cc. 
N/10 solution when acting as an oxidizing agent. 

52 (atomic weight of chromium) -— 3 = 17.3 grams Cr 
in 1 liter of solution. 

(218) 

(c) Assume bath is all // 2 O 2 7 . — H 2 Cr 2 7 -f - 6KI -f- 

(762) 
12HC1 = 2CrCl 3 + 6KC1 +7H 2 + "~6I~ 

218 : 762 : : 1 : x; x = 3.498 grams of I liberated by 1 
gram of H 2 Cr 2 7 . 

n 019 - = 275.4 cc. N/10 Na 2 S 2 3 necessary to absorb the 
iodine liberated by 1 gram of [see explanation in (a)] H 2 Cr 2 07. 
(218) (160) 

H 2 Cr 2 7 + 4NaOH = 2Na 2 Cr0 4 + 3H 2 0. 

218 : 160 :: 1 : x; x = 0.7339 gram NaOH necessary 
to react with 1 gram of H 2 Cr 2 7 (H 2 Cr 2 7 does not exist 
out of solution). 

7339 
' nft . = 183.5 cc. N/10 NaOH necessary to react with 1 

gram of H 2 Cr 2 7 . 



606 PRACTICAL TANNING 

183.5 is | of 275.4, therefore when the bath is all H2Cr207 the 
cc. of N/10 NaOH = § cc. N/10 Na 2 S 2 3 . 

Strength.— cc. N/10 Na 2 S 2 3 X 0.00333 X 50 == grams 
CrOs (as H 2 Cr 2 07) per 100 cc. of solution. 

(Note: 0.0033 = grams Cr0 3 per cc. N/10 solution.) 

100 (mol. wt.) CrOs -r-3 = 33.3 grams Cr0 3 per liter of 
normal solution. 

(d) Assume bath is a mixture of H^CriOi and Na^Cr^Oi. — 
Both of these react with the NaOH and Na 2 S 2 3 . Then cc. 
N/10 NaOH = § and \ cc. N/10 Na 2 S 2 3 . 

Strength. — 

Let a = cc. N/10 Na 2 S 2 3 for Na 2 Cr 2 7 and H 2 Cr 2 7 . 

a u _ « u u u u 

" c = " " " " H 2 Cr 2 7 .' 

(1) Thenb + c = a. 

Let a' = cc. N/10 NaOH for Na 2 Cr 2 7 and H 2 Cr 2 7 . 

u u/ __ « u a « <* 

" c' = " " " " H 2 Cr 2 7 . ' 

(2) Then b' + c' = a. 

But Na 2 Cr 2 07 requires 3 times as many cc. of N/10 
Na 2 S 2 3 as it does cc. of N/10 NaOH. 

(3) Therefore, b' = | 

Also H 2 Cr 2 07 requires f as many cc. of N/10 NaOH as cc. 
of N/10 Na 2 S 2 3 . 

2c 

(4) Therefore, c = -^ * 

In equation (2) substitute (3) and (4), therefore 
b 2c 

3 + T = a or 

(5) b + 2c = 3a 

(6) From (1) we get b = a — c. 
Substitute (6) in (5) 

a — c + 2c = 3a' or a -f- c = 3a' of 



ANALYTICAL METHODS 607 

c = 3a' — a. This gives cc. N/10 Na 2 S 2 3 used for 
H 2 2 7 . 

a — c = b cc. N/10 Na 2 S 2 03 used for Na 2 Cr 2 7 . 

Strength.— cc. N/10 Na 2 S 2 O a (c) X 0.0033 X 50 = 
grams Cr0 3 (as H 2 Cr 2 T ) per 100 cc. of solution. 
5 cc. N/10 Na 2 S 2 O s (b) X 0.00436 X 50 = grams Na 2 Cr 2 7 
per 100 cc. of solution. 

(e) When bath contains free acid (HC1 or H2SO4). — 
Under these conditions all chromium will be in the form of 
H 2 Cr 2 7 and the cc. N/10 NaOH = § cc. N/10 Na 2 S 2 C 3 . 

Strength.— cc. N/10 Na 2 S 2 O a X 0.0033 X 50 = grams 
Cr0 3 as H 2 Cr 2 7 per 100 cc. 

Since for H 2 Cr 2 7 the cc. N/10 NaOH = § cc. N/10 
Na 2 S 2 3 . 

Then, cc. N/10 NaOH — § cc. N/10 Na 2 S 2 3 = x cc. 
N/10 NaOH to neutralize free acid. 

x X 0.00365 X 10 = grams HC1 in 100 cc. 

x X 0.0049 X 10 = grams H 2 S0 4 in 100 cc. 

iVajj^Os in hypo bath. — Place 10 cc. of 10 per cent potas- 
sium iodide solution, 5 cc. of concentrated hydrochloric acid, 
and 25 cc. of N/10 K 2 Cr 2 7 , in a 250 cc. glass-stoppered 
bottle. Place the hypo solution in a burette and titrate the 
liberated iodine in the bottle, using starch as an indicator. 
The volume of hypo required contains 0.620 grams of pure 
Na 2 S 2 3 .5H 2 0. Its strength would be 

XT '^ X 100 = grams Na 2 S 2 3 .5H 2 per 100 cc. 

cc. Na 2 S 2 3 used. 

(Note: 1 cc. N/10 K 2 Cr 2 7 == 1 cc. N/10 iodine 

solution.) 

1 cc. N/10 iodine solution contains 0.0127 gram of iodine. 

0.0127 X 25 = 0.3175 gram of iodine liberated. 

(496) (254) 

2Na 2 S 2 3 .5H 2 + I 2 = Na 2 S 4 6 + 2NaI. 

496 : 254 :: x : 0.3175. 

x = 0.620 gram of Na 2 S 2 3 .5H 2 in the amount of sam- 
ple taken. 



608 PRACTICAL TANNING 

Second bath when made up of NaHS0 3 . — Determination of 
NaHS0 3 : The method is the same as that for Na2S203 in 
hypo bath. 

0.130 X 100 
ocNaHSO, solution used = gramS of NaHS ° 3 P er 10 ° cc ' of 
solution. 

(Note: 1 cc. N/10 K 2 Cr 2 7 = 0.0127 gram of I.) 

0.0127 X 25 = 0.3175 gram of I liberated. 

(104) (254) 
NaHS0 3 + I 2 + H 2 = NaHS0 4 + 2HI. 

104 : 254 :: x : 0.3175. 

x — 0.130 gram of NaHSOs in cc. of sample taken. 

One-bath chrome liquor: 1. Determination of chrom- 
ium. — Reagents used are as follows: 

N/10 Na 2 S 2 3 solution 1 cc. = 0.00173 gram Cr. 

10 per cent potassium iodide solution. 

Starch solution, 1 gram starch per 100 cc. of water, pre- 
served with formaldehyde. 

Concentrated hydrochloric acid. 

Sodium peroxide. 

Standard N/10 sodium hydroxide. 

Phenolphthalein, 1 gram per 100 cc. alcohol. 

(a) Determination of Cr in new or spent liquor. — Pipette 
10 cc. into an Erlenmeyer flask, to which add 125 cc. of water 
and 3 grams of sodium peroxide ; add the latter in small por- 
tions. Boil the mixture for a half-hour, adding more water if 
necessary. 

Transfer the yellow solution to a 500 cc. beaker; rinsing 
the Erlenmeyer several times with water. Cool thoroughly, 
then add 8 cc. of concentrated hydrochloric acid and 10 cc. 
of potassium iodide solution, and let stand five minutes. The 
solution must now be perfectly clear and reddish-brown in 
color. If black particles float on top, more potassium iodide 
solution is required. If the solution is still yellow or light 
brown, more acid must be added. Now run in sodium thiosul- 
phate solution from a burette with constant stirring until the 



ANALYTICAL METHODS 609 

color has changed to a light brown. Then add a few drops 
of starch indicator after which an intense blue coloration 
should ensue. Dilute to 400 cc, and add more sodium thiosul- 
phate solution, drop by drop, with constant shaking until the 
blue color changes to a permanent light green. 

No. cc. N/10 Na^Os X 0.00173 X 100 

Strength. ■ ~iq 

or 

No. cc. N/10 Na 2 S 2 3 X 0.0173 = grams Cr per 100 cc. 

(b) Determination of Cr in stock liquor.— Pipette 10 cc. 
of stock chrome liquor into a 500 cc. graduated flask, make up 
to the mark with water and mix thoroughly by shaking. Pi- 
pette off 25 cc. of this diluted solution for analysis. Follow 
the directions given above. 

Strength.— No. cc. N/10 Na 2 S 2 O s X 0.00173 X 200 = 
grams of Cr per 100 cc. of liquor. 

(c) Determination of basicity for diluted chrome liquors — 
Pipette 10 cc. original liquor into a casserole and add about 125 
cc of water. Heat to boiling and add 1 cc. phenolphthalein, 
then run in standard sodium hydroxide from burette with 
constant stirring until the supernatant liquid shows a faint 
pink coloration. 

cc. N/10 NaOH X 0.0048 X 10 

° cc. N/10 NaOH X 0.048 = grams of S0 4 per 100 cc. 

(d) Determination of basicity of stock liquor.— Pipette 
10 cc. of stock chrome liquor into a 500 cc. graduated flask, 
make up to mark with water and mix thoroughly by shaking. 
Pipette off 25 cc. of this diluted solution for analysis. Fol- 
low directions as given above. 

Strength.— cc. N/10 NaOH X 0.0048 X 200 

cc. N/10 NaOH X 0.96 = grams of S0 4 per 100 cc. 

2 Use of above results to obtain correct basicity of one- 
bath chrome liquors.— -The best salts for tanning purposes are 
the basic salts Cr 2 (OH) 2 (S0 4 )2 or Cr 2 Cl 3 (OH) 3 . 



610 PRACTICAL TANNING 

The ratio of Cr to SO3 is 104 : 160 or as 52 : 80. From 
the analysis of the liquor determine the ratio of Cr to SO3 
by the proportion 

grams Cr in 100 cc. 52 . __ . . , . , 

^r~- — tt^ = — ; x = grams of S0 3 combined with 

grams S0 3 m 100 cc. x 

52 grams of Cr. 

If the ratio is above 80 there is too much acid present, and 
sodium carbonate must be added to bring down the ratio to 
52:80, while if the ratio is below 80, sulphuric acid must be 
added to bring the ratio up to standard. 

(a) Assume the analysis shows the ratio to be 52 : 83.2. — 

80 
When ratio is 52 :80; 1 gram of Cr == 52 or 1.54 grams SO3 ; 

83.2 
and when ratio is 52 : 83.2; 1 gram Cr = 52 or 1.6 grams SO3. 

1.6 — 1.54 = 0.06 gram SO3 to be neutralized for each 
gram of Cr present. 

(98) (286) 

H 2 S0 4 + Na 2 CO 3 .10H 2 O = Na 2 S0 4 + H 2 + C0 2 + 10H 2 O. 

Na 2 CO 3 .10H 2 O (286) x 286 X 1 

"SO* "l80y = T ; X = ~~80— ; x = 3 - 58 S rams of 

Na 2 CO 3 .10H 2 O necessary for every gram of S0 3 to be neutralized. 

0.06 X 3.58 = 0.2148 gram of Na 2 CO 3 .10H 2 for each 
gram of Cr. 

(cc. in gal.) 
grams Cr in 100 cc. X 3785 X 0.2148 , , .. __ 

453.6 X 100 = P ° Unds ° f Na2C ° 3 

(grams in 1 lb.) 

10H 2 O to be added per gallon. 

Summary. — When the grams of SO3 per one gram of chrom- 
ium are greater than 1.54, subtract 1.54 from this value and 
substitute the result in the equation given below. 

grams Cr in 100 cc. X 37.85 X ? 
453.6 
or 

grams Cr in 100 cc. X 0.0834 X ? = pounds of Na 2 CO 3 .10H 2 O 
to be added per gallon to give the desired basicity. 



ANALYTICAL METHODS 611 

(b) Assume the ratio is below 80, say 69.16. — Then 1 
gram of Cr is combined with 

69.16 



52 



= 1.33 grams S0 3 . 



1.54 — 1.33 = 0.21 gram of SO3 to be added for each 
gram of Cr. 

grams Cr in 100 cc. X 3785 X 0.21 X 1 , , 
453 6 x 10() =' pounds of sul- 

phuric acid to be added per gallon. 

a m oun t H3SO 4i n llb .co X mm e re ,a, a c ld (0.93 51b .) = *-— 

commercial acid to be added. 



Summary. — When the grams of SO3 per one gram of Cr 
are less than 1.54, subtract this value from 1.54 and substitute 
the result in the equation given below. 

grams Cr in 100 cc. X 46.366 X ? 
424.1 
or 

grams of Cr in 100 cc. X 0.1117 X ? = pounds of commer- 
cial H2SO4 to be added per gallon of solution to give proper 
basicity. 

Vegetable tanning materials. — The following are the 
quantities of the materials to be taken for analysis : 

Unextracted materials 

Graves Cubic centimeters 

Myrabolans 20 2000 

Valonia cups 20 2000 

Divi divi 20 2000 

Sumac 20 2000 

Oak bark 30 1000 

Hemlock 30 1000 

Chestnut wood 50 1000 

Spent tans 50 1000 



612 PRACTICAL TANNING 

Extracts 

Grams Cubic centimeters 

Chestnut 35 to 45° Be 14 1000 

45 to 60° Be 12 1000 

Mynabolans to 50° Be 14 1000 

50 to 100° Be 13 1000 

Mangrove to 50° Be 14 1000 

50 to 100° Be 13 1000 

Quebracho (solid) 12 1000 

Myrabolans (solid) 14-15 1000 

Mangrove (solid) 14-15 1000 

Cutch (solid) 14-15 1000 

Quebracho (solid) 12 1000 

Tan liquors 

Cubic centimeters Cubic centimeters 

Barkometer reading to 15° 200 1000 

15 to 25° 100 1000 

25 to 40° 50 1000 

40 to 60° 25 1000 

Above 60° bk. weigh out 15 to 20 grams, according to 
strength, and dilute to 1000 cc. 

The following corrections should be applied to the barkom- 
eter readings: At 70° F. add 1.0 to the reading; at 75° add 
1.5; at 80° add 2.0. When the reading is 30 or above, and 
the temperature is 80° F. or more, add 2.5. 

The following determinations are made: 

1. Total solids. 

2. Soluble solids. 

3. Insoluble solids. 

4. Tannins. 

5. Non-tannins. 

6. Specific gravity by Westphal balance at 15.5° C. 

OFFICIAL METHOD OF THE AMERICAN LEATHER CHEM- 
ISTS' ASSOCIATION FOR THE ANALYSIS OF VEGE- 
TABLE MATERIALS CONTAINING TANNIN 

I. Raw and spent materials 

(1) Caution. — Proper care must be taken to prevent any 
change in the water content of raw materials during the 
sampling and preliminary operations. (See "General" under 
"Sampling.") 



ANALYTICAL METHODS 



613 



(2) Preparation of sample. — The sample must be ground 
to such a degree of fineness that the entire sample will pass 
through a sieve of 20 meshes to the linear inch. 

(a) The temperature used for drying samples of spent 
material for grinding must not exceed 60° C. 

(b) Samples of raw material too wet 
to be ground may be dried before grinding 
as in (a). In this case a preliminary 
water determination must be made ac- 
cording to (IV) on the sample as re- 
ceived. If the portion of the sample taken 
for the water determination is in pieces 
too large to dry properly, it is permissible 
to reduce these to smaller size as rapidly 
and with as little loss of water as possible. 

(3) Water determination. — Ten grams 
of the ground material shall be dried in 
the manner and for the period specified 
for evaporation and drying in extract 
analysis. 

(4) Amount of sample to be extracted. 
— Such an amount of raw material shall 
be extracted as will give a solution con- 
taining as nearly as practicable 0.4 gram 
tannin to 100 cc. (not less than 0.375 nor 
more th,an 0.425). Of spent materials 
such an amount shall be taken as will give 

p. —Tea's a som ^ on °f as nearly as practicable the 

extractor. above concentration. 




(5) Extraction. — This shall be conducted in an apparatus 
(figure 123) consisting of a vessel in which water may be 
boiled and a container for the material to be extracted. The 
container shall be provided above with a condensation chamber 
so arranged that the water formed from the condensed steam 
shall drip on the material to be extracted, and provided below 
with an arrangement of outlets such that the percolate may 
either be removed from the apparatus or be delivered to the 



614 PRACTICAL TANNING 

boiling vessel. The boiling vessel must be so connected that it 
will deliver steam to the condensation chamber and that it may 
receive the percolate from the container. The condensation 
water from the condenser must be at approximately the boiling 
temperature when it comes in contact with the material to be 
extracted. 

The material of which the boiling flask is composed must 
be inert to the extractive solution. Suitable provision must 
be made for preventing any of the solid particles of the ma- 
terial from passing into the percolate. 

(A) Woods, barks and spent materials : 

Five hundred cc. of the percolate shall be collected outside in 
approximately 2 hours and the extraction continued with 500 
cc. for 14 hours longer by the process of continuous extraction 
with reflux condenser. The applied heat shall be such as to 
give condensation of approximately 500 cc. in 1^ hours. 

(B) Materials other than woods, barks and spent: 

Digest the material in the extractor for 1 hour with water 
at room temperature, and then extract by collecting 2 liters 
of percolate outside in approximately 7 hours. 

(6) Analysis. — The percolate shall be heated to 80° C, 
cooled, made to the mark, and analyzed according to the 
official method of extracts. 

II. Analysis of extract 

(7) 'Amount and dilution for analysis. — 

(A) Fluid extracts: These shall be allowed to come to 
room temperature, mixed thoroughly, and such quantity 
weighed for analysis as will give a solution containing as 
nearly as possible 0.4 gram tannin to 100 cc. (not less than 
0.375 nor more than 0.425). Precautions must be taken to 
prevent loss of moisture during weighing. Dissolve the extract 
by washing it into a liter flask with 900 cc. of distilled water 
at 85° C. 



ANALYTICAL METHODS 615 

Cooling : 

(a) The solutions prepared as above shall be cooled rapidly 
to 20° C. with water at a temperature of not less than 19° C, 
be made to the mark with water at 20° C. and the analysis 
proceeded with at once, or 

(b) The solution shall be allowed to stand over night, the 
temperature of the solution not being permitted to go below 
20° C, be brought to 20° C. with water at not less than 19° 
C, be made to the mark with water at 20° C, and the analysis 
proceeded with. 

(B) Solid and powdered extracts: Such an amount of 
solid or powdered extract as will give a solution of the strength 
called for under liquid extracts shall be weighed in a beaker 
with proper precautions to prevent change of moisture. One 
hundred cubic centimeters of distilled water at 85° C. shall 
be added to the extract and the mixture placed on the water- 
bath, heated, and stirred until a homogeneous solution is ob- 
tained. When dissolved, the solution shall immediately be 
washed into a liter flask with 800 cc. of distilled water at 85° 
C, be cooled, etc., as under (A) above. 

(Note: It is permissible to make up 2-liter instead of 1-liter 
solutions, dissolving by washing into flask with 1,800 cc. water 
at 85° C. in case of fluid extracts and 1,700 cc. water at 
85° C. in case of solid or powdered extracts.) 

(8) Total solids. — Thoroughly mix the solutions; pipette 
100 cc. into tared dish, evaporate and dry as directed under 
"Evaporation and Drying." (See IV.) 

(9) Water. — The water content is shown by the difference 
between 100 per cent and the total solids. 

(10) Soluble solids.— S. & S. No. 590, or Munktell's No. 
IF, 15 cm. single-pleated filter-paper shall be used for the 
filtration. 

The kaolin used shall answer the following test: 2 grams 
of kaolin digested with 200 cc. of distilled water at 20° C. 
for 1 hour shall give not more than 1 mg. of soluble solids 
per 100 cc, and shall be neutral to phenolphthalein. To 1 



616 PRACTICAL TANNING 

gram of kaolin in a beaker add sufficient solution to fill the 
paper, stir, and pour on paper. Return filtrate to paper when 
approximately 25 cc. has collected, repeating operation for 1 
hour, being careful to transfer all kaolin to the paper. At 
the end of the hour remove solution from filter-paper, dis- 
turbing the kaolin as little as possible. Bring as much as 
needed of the original solution to exactly 20° C„ as described 
under (7), re-fill the paper with this solution and begin to 
collect the filtrate for evaporating and drying as soon as it 
comes clear. The paper must be kept full, and the tempera- 
ture of the solution on the filter must not fall below 20° C. 
nor rise above 25° C. during this part of the filtration. The 
temperature of the solution used for re-filling the paper must 
be kept uniformly at 20° C, and the funnels and receiving 
vessels must be kept covered. 

Pipette 100 cc. of clear filtrate into tared dish; evaporate 
and dry as under (8). 

(11) Insolubles. — The insoluble content is shown by the 
difference between the total solids and the soluble solids, and 
represents the matter insoluble in a solution of the concentra- 
tion used under the temperature conditions prescribed. 

(12) Non-tannins. — The hide powder used for the non- 
tannin determination shall be of wooly texture, well de-limed, 
and shall require between 12 and 13 cc. of N/10 NaOH to 
neutralize 10 grams of the absolutely dry powder. 

(a) Digest the hide powder with 10 times its weight of 
distilled water till thoroughly soaked. Add 3 per cent of 
chrome-alum (Cr 2 S04)3K 2 S04.24H 2 0, in 3 per cent solution 
calculated on the weight of the air-dry powder. Agitate fre- 
quently for several hours, and let stand over night. Squeeze 
and wash by digesting in the cold with 4 successive portions 
of distilled water, each portion equal in amount to 15 times 
the weight of the air-dry powder taken. Each digestion shall 
last for 15 minutes, and the hide powder shall be squeezed 
to approximately 75 per cent water after each digestion ex- 
cept the last, a press being used if necessary. The wet hide 
powder used for the analysis shall contain as nearly as pos- 



ANALYTICAL METHODS 617 

sible 73 per cent of water, not less than 71 per cent nor 
more than 74 per cent. Determine the moisture in the wet 
hide powder by drying approximately 20 grams (see IV). 
To such quantity of the wet hide as represents as closely as 
practicable 12} grams (not less than 12.2 nor more than 12.8) 
of absolutely dry hide, add 200 cc. of the original analysis 
solution and shake immediately for 10 minutes in some form 
of mechanical agitator. Squeeze immediately through linen, 
add 2 grams of kaolin (answering test described under 9) 
to the de-tannized solution and filter through single- folded filter 
(No. IF Swedish recommended) of size sufficient to hold 
the entire filtrate, returning until clear. Pipette 100 cc. of 
filtrate into tared dish, evaporate and dry as in (8). 

The weight of the non-tannin residue must be corrected 
for the dilution caused by the water contained in the wet 
hide powder. 

Funnels and receiving vessels must be kept covered dur- 
ing filtration. Flasks graduated to deliver 200 cc. are rec- 
commended for measuring the analysis solution to be 
detannized. 

(b) Digest the hide powder in the cold with the amount 
of water and add the amount of chrome-alum in solution 
directed under (a). 

Agitate by some form of mechanical apparatus for 1 hour. 
and proceed immediately with washing and subsequent opera- 
tions as directed under (a). 

(Note: In order to limit the amount of dry hide powder 
used, determine the moisture in the air-dry powder and cal- 
culate the quantity equal to \2\ grams of actual dry hide 
powder. Take any multiple of this quantity according to 
the number of analyses to be made, and after chroming^and 
washing as directed, squeeze to a weight representing as 
nearly as possible 73 per cent of water. Weigh the whole 
amount, and divide by the multiple of the \2\ grams of 
actual dry powder taken to obtain the weight of wet hide 
powder for 200 cc. of solution.) 



618 PEACTICAL TANNING 

(13) Tannin. — The tannin content is shown by the dif- 
ference between the soluble solids and the corrected non-tan- 
nins, and represents the matters absorbable by hide under the 
conditions of the prescribed methods. 

III. Analysis of liquor 

(14) Dilution. — Liquors shall be diluted for analysis with 
water at room temperature so as to give as nearly as pos- 
sible 0.7 gram of solids per 100 cc. of solution. Should a 
liquor be of such character as not to give a proper solution 
with water of room temperature it is permissible to dilute 
with water at 80° C. and cool rapidly as described under 
(7, A, a). 

(15) Total solids. — To be determined as in Extract 
Analysis. 

(16) Soluble solids. — To be determined as in Extract 
Analysis. 

(17) Insolubles. — To be determined as in Extract Analysis. 

(18) Non-tannins. — To be determined by shaking 200 cc. 
of solution with an amount of wet chromed hide powder, 
containing as nearly as possible 73 per cent water, correspond- 
ing to an amount of dry hide powder shown in the following 
table : 

Tannin range per 100 cc. Dry powder per 200 cc. 
Gram Grams 

0.35—0.45 9.0—11.0 

0.25—0.35 6.5— 9.0 

0.15—0.25 4.0— 6.5 

0.00—0.15 0.0— 4.0 

Solutions to be shaken for non-tannins as in Extract An- 
alysis and 100 cc. evaporated as in Extract Analysis. 

IV. Temperature, evaporation and drying, and dishes 

(19) Temperature. — The temperature of the several por- 
tions of each solution pipetted for evaporating and drying, 
that is, of the total solids, soluble solids and non-tannins, must 
be identical at the time of pipetting. 



ANALYTICAL METHODS 619 

(20) Evaporation. — All evaporations and dryings shall be 
conducted in the form of apparatus known as the "combined 
evaporator and dryer" (figure 124) at a temperature not less 
than 98° C. The time for evaporation and drying shall be 
16 hours. 

(21) Dishes. — The dishes used for evaporation and drying 









^^ 




>5> 


It • 




i 




jfcti *m 






JH 




i 



Figure 124. — Combined evaporator and dryer. 

of all residues shall be flat-bottomed glass dishes not less 
than 2f inches nor more than 3 inches in diameter. 

V. Determination of total acidity of liquors 
(22) Reagents. — (a) One per cent solution of gelatine 
neutral to hematin. The addition of 25 cc. of 95 per cent 
alcohol per liter is recommended to prevent frothing. If the 
gelatine solution is alkaline, neutralize with tenth normal acetic 
acid, and if acid, neutralize with tenth normal sodium 
hydroxide. 

(b) Hematin. A solution made by digesting hematin in 
cold neutral 95 per cent alcohol in the proportion of ^ gram 
of the former to 100 cc. of the latter. 



620 PRACTICAL TANNING 

(e) Acid-washed kaolin free from soluble matters. 

(d) Tenth normal sodium hydroxide. 

Directions. — To 25 cc. of the liquor in a cylinder that can be 
stoppered, add 50 cc. of gelatine solution, dilute with water 
to 250 gc., add 15 grams of kaolin and shake vigorously. 
Allow to settle for at least 15 minutes, remove 30 cc. of the 
supernatant solution, dilute with 50 cc. of water, and titrate 
with tenth normal soda, using hematin solution as the indi- 
cator. Each cubic centimeter of tenth normal soda is equiv- 
alent to 0.2 per cent acid as acetic. 

VI. General 

(23) When materials containing sulphite cellulose extract 
are analyzed, the fact that the material contains this extract 
shall be noted in the report. 

(24) The test for the presence of sulphite cellulose in a 
liquor or extract shall be as follows: 5 cc. of a solution of 
analytical strength shall be placed in a test-tube, 0.5 cc. of 
aniline added and the whole well shaken ; then 2 cc. of strong 
hydrochloric acid added and the mixture again shaken. If at 
least as much precipitate remains as is obtained when a com- 
parison solution prepared as below is similarly treated, the 
material shall be held to contain sulphite cellulose. (Neradol 
D gives the same reaction.) 

The comparison solution shall consist of sulphite cellulose 
in the proportion of 1 part total solids to 2,000 cc. of solu- 
tion, and as much tanning material, similar to that being 
tested, but known to be free from sulphite cellulose, as will 
make up the solution to analytical strength. 

(25) On public analytical work by members of this As- 
sociation the fact that the official method has been used shall 
be stated. 

OFFICIAL METHOD FOR SAMPLING TANNING MATERIALS 

General. — Extract, whether liquid or solid, and tanning ma- 
terials in general, all contain moisture. The amount of mois- 



ANALYTICAL METHODS 621 

ture varies with climatic conditions, but especially in liquid, 
and in most solid extracts becomes less as the extract is ex- 
posed to the air. As the value of any material shown by 
analysis is directly dependent upon the amount of moisture 
contained, and as an exposure of a comparatively few mo- 
ments may alter appreciably the amount of moisture, it is ap- 
parent that the sampling in all its details should be done as 
quickly as consistent with thoroughness and with great care to 
expose the material as little as possible to the air. The por- 
tions taken as samples should be placed at once in containers 
as nearly air-tight as possible, and preferably of glass. Wood, 
cardboard, poorly glazed crockery, etc., are all porous and 
more or less absorbent and not suitable for retaining samples. 

Liquid extract cannot be accurately sampled when it con- 
tains any frozen material. A sample of extract taken after 
live steam has been run into the extract has not the same 
concentration as the original extract. A sample of spent 
bark which has been standing where dust from freshly ground 
bark has sifted into it does not represent the degree of ex- 
traction of the spent bark. Samples of liquor which have been 
kept with no preservative in them for some time do not rep- 
resent the condition of the liquor when sampled. 

All extracts and crude tanning materials shall be sampled 
as nearly as possible at time of weighing, and for every 50,000 
lb. or less sampled, a sample shall be drawn. 

(1) Solid, powdered and pasty extracts. — The number of 
packages to be sampled out of a given lot shall be ascertained 
by taking a percentage of the total number of packages in 
the lot obtained in the following manner : Divide the total 
number of packages by 100, multiply by 0.02, and subtract 
from 4. 

Thus 4,700 -=- 100 = 47 

47 X 0.02 = 0.94 

4 — 0.94 = 3.06 per cent 

4,700 X 0.0306 = 144 packages 



622 PRACTICAL TANNING 

Provided that for lots of 200 packages and under, 5 per 
cent of the number of packages shall be sampled; and for lots 
of 10,000 packages and over, 2 per cent of the number of 
packages shall be sampled. 

Whenever possible every iVth package shall be set aside for 
sampling while the extract is being moved. When this is not 
possible, the packages shall be selected from as uniformly 
distributed parts of the bulk as possible. 

Samples of as nearly equal size as practicable shall be taken 
from each package, and these samples shall represent as nearly 
as may be, proportionally the outer and inner portions of the 
extract. These sub-samples shall be placed in a clean, dry, 
closed container. When sampling is completed, the whole 
composite sample shall be broken up until it will pass through 
a sieve of 1-inch mesh; it shall be reduced to the required bulk 
by successive mixings and quarterings. From this bulk, du- 
plicate samples of at least 6 ounces shall be drawn from op- 
posite quarters by means of a small flat scoop (and not by 
selecting a handful here and there). The sample shall be 
enclosed in the smallest clean, dry, glass receptacle, sealed 
and properly labeled. 

(Note: Whenever possible, the sample should be wrapped 
in paraffin paper and placed in the smallest straight-side glass 
receptacle ; especially is this desirable during the warmer 
months of the year.) 

Sampling at place of manufacture shall be conducted by 
running a portion from the middle of each strike into a mold 
holding at least 2 lb. These sub-samples shall be preserved 
with proper precautions against evaporation, and be sampled 
for analysis as above. 

(2) Liquid extracts in barrels. — The number of barrels of 
extracts to be sampled out of any given lot shall be not less 
than 10 per cent of the whole number of barrels for every 
50,000 lb. or fraction thereof. The barrels to be sampled 
shall be rolled and shaken from end to end until the contents 
are homogeneous. Whenever this is not possible the heads 



ANALYTICAL METHODS 623 

of the barrels shall be removed and the contents stirred until 
homogeneous, a sample of equal size to be taken from each 
barrel. These sub-samples shall be put together in a suitable 
closed container and thoroughly mixed. From this bulk, du- 
plicate samples of at least 4 oz. shall be drawn and preserved 
in clean, dry, glass containers; sealed and labeled with such 
distinguishing marks as may be necessary. 

(3) Liquid extract in bulk. — The extract shall be agitated 
with air, plunged or mixed by some other efficient means until 
homogeneous. Equal samples shall then be taken from dif- 
ferent parts of the bulk, placed in a proper container, thor- 
oughly mixed, and sampled as described in (2). 

(4) Liquid extract in tank-cars. — The following methods 
are permissible : 

(a) The extract shall be unloaded into clean, dry contain- 
ers and sampled according to (3). 

(b) The extract shall be mixed until homogeneous, by 
plunging through the dome or other effective means, then 
numerous equal samples shall be taken from as widely scat- 
tered parts of the bulk as possible. These samples shall then 
be placed in a suitable container, be mixed and sampled as 
in (2). 

(Note : As it is almost impossible to secure a homogeneous 
mixture of the extract in a tank-car, this method should be 
used only when no other is possible.) 

(c) The extract shall be sampled as follows while the car 
is being unloaded: A quart sample shall be taken from the 
discharge three minutes after the extract has begun to run; 
another quart sample shall be taken three minutes before the 
extract has all run out, and three other quart samples shall be 
taken at equal intervals between these two. These five sam- 
ples shall be transferred to a suitable container as soon as 
taken, be thoroughly mixed and sampled as in (2). 

(5) Crude tanning materials. — (A) Shipments in bags, 
mats or other similar packages. 

A number of packages shall be sampled representing 2 per 



624 PRACTICAL TANNING 

cent of the weight for every shipment of 50,000 lb. or frac- 
tion thereof, by taking representative portions from each 
package. These sub-samples shall be mixed together and the 
bulk reduced by mixing and quartering to the desired size. 
Duplicate samples of not less than 5 lb. each shall be preserved 
in air-tight containers properly labeled. 

(B) Shipments in bulk, bark, wood, etc., in sticks. 

Sticks shall be taken from at least ten uniformly distributed 
parts of the bulk, sawed completely through, and the sawdust 
thoroughly mixed and sampled as in A. 

(C) Materials prepared for leaching. 

Samples of equal size shall be taken at uniform intervals 
as the material enters the leach and be kept in a suitable con- 
tainer till sampling is completed. This bulk shall then be 
thoroughly mixed, be reduced by mixing and quartering, and. 
duplicate samples for analysis of at least 2 lb. in size be pre- 
served in air-tight containers, as in A. 

(6) Spent materials from leaches. — Samples of spent ma- 
terial shall be taken from the top, middle, and bottom, and in 
each case from the center and outer portions of the leach. 
These sub-samples shall be thoroughly mixed, reduced in bulk 
by mixing and quartering, and duplicate samples of at least 
1 quart in size preserved for analysis. 

(7) Tanning liquors. — The liquor shall be mixed by plung- 
ing or other effective means till homogeneous and then sam- 
ples of at least 1 pint be taken for analysis. The addition of 
0.03 per cent of thymol or other suitable anti-ferment to the 
sample is essential to keep the liquor from altering its orig- 
inal condition. 

When routine samples are taken from day to day and a 
composite sample analyzed, samples of equal size shall be taken 
from each vat after thorough mixing, preserved in covered 
containers in as cool a place as possible, and kept from fermen- 
tation by the addition of suitable anti-ferment, as above. This 
bulk shall be mixed till homogeneous, and samples of not less 
than 1 pint each preserved for analysis. 



ANALYTICAL METHODS 625 

When a sample is taken by a member of this Association 
in accordance with the above method, it is requested that he 
state on the label of the sample submitted and on the analysis 
blank that "this sample has been taken in accordance with the 
official method of sampling of The American Leather Chem- 
ists' Association." 

OFFICIAL METHOD FOR ANALYSIS OF VEGETABLE- 
TANNED LEATHER 

(1) Preparation of sample.— The sample of leather for 
analysis shall be reduced to as fine a state of division as prac- 
ticable, either by cutting or grinding. 

(2) Moisture. — Dry 10 grams of leather for 16 hours at 
a temperature between 95 and 100° C. 

(3) Fats.— Extract 5 to 10 grams of air-dry leather in 
a Soxhlet apparatus until free from grease, using petroleum 
ether boiling below 80° C. Evaporate off the ether and dry 
to approximately constant weight. 

Or, if preferred, extract 30 grams of leather as described 
above. In the latter case, the extracted leather, when freed 
of solvent, may be used for the determination of water-solu- 
ble material. 

(4) Ash. — Incinerate 10 to 15 grams of leather in a tared 
dish at a dull red heat until carbon is consumed. If it is 
difficult to burn off all the carbon, treat the ash with hot 
water, filter through an ashless filter, ignite filter and residue. 
Add the filtrate, evaporate to dryness, and ignite. 

(5) Water-soluble material. — Digest 30 grams of leather 
in a percolator over night, then extract with water at 50° C. 
for 3 hours, the total volume of the solution to be 2 liters. 
Determine total solids and non-tannins according to the of- 
ficial method for Extract Analysis. 

(6) Glucose. — 

Solutions 

Copper sulphate. — Dissolve 34.639 grams of CuS0 4 .5H 2 
in distilled water and dilute to 500 cc. Filter through asbestos. 



626 PRACTICAL TANNING 

Alkaline tartrate solution. — Dissolve 173 grams of Ro- 
chelle salt and 50 grams NaOH in water and dilute to 500 cc. 
Allow to stand 2 days and filter through asbestos. 

Normal lead acetate solution. — Prepare a saturated solution 
of normal lead acetate. 

Determination 

Place 200 cc. of leather extract of analytical strength in 
a -|-liter flask, add 25 cc. of a saturated solution of normal 
lead acetate, shake frequently (5 to 10 minutes), and filter. 
(The funnels and beakers must be kept covered to prevent 
evaporation.) Add to the filtrate an excess of solid potas- 
sium oxalate. Mix frequently for 15 minutes and filter, re- 
turning the filtrate until clear. Pipette 150 cc. of this filtrate 
into a 600 cc. Erlenmeyer flask, add 5 cc. of concentrated 
HC1 and boil under a reflux condenser for 2 hours. Cool, 
neutralize (place a small piece of litmus paper in the flask) 
with anhydrous sodium carbonate, transfer to a 200 cc. grad- 
uated flask, and make to volume. Filter through a double 
filter (the filtrate must be clear). Determine the dextrose in 
the solution immediately. 

Place 25 cc. of the copper solution and 25 cc. of the alkaline 
tartrate solution in a 400 cc. beaker. Add 50 cc. of the clar- 
ified and neutralized solution above mentioned, and heat to 
boiling in exactly 4 minutes and boil for 2 minutes. 1 Filter 
immediately without diluting, through asbestos, 2 wash thor- 
oughly with hot water, then with alcohol, and finally with 
ether; dry for ^ hour in water-oven, and weigh as cuprous 
oxide, determine the amount of dextrose by the use of Mun- 
son and Walker's table, and report in percentage on leather. 



1 The rate of heating of the Bunsen burner used should be regulated before sugar 
determinations are started. This is best done by adjusting the burner so as to 
bring 25 cc. copper solution + 25 cc. alkaline tartrate solution + 50 cc. H 2 in 
a 400 cc. beaker to 100° C. in exactly four minutes. 

2 The finely divided, long-fibered asbestos to be used in the glucose determination 
should be digested with HN0 3 , washed, then digested with NaOH and washed. 
When Gooch filters are prepared, they should be washed with boiling Fehling's 
solution, then with HNO3. The mats thus prepared can be used for a long time. 



ANALYTICAL METHODS 



627 



Munson and Walker's Table 

(Bulletin 107 [Revised], Bureau of Chemistry, page 243.) 
(Expressed in milligrams.) 



Cuprous 
oxide 


Copper 


Dextrose 


Cuprous 
oxide 


Copper 


Dextrose 


(Cu 2 0) 


(Cu) 


(d-glucose) 


(Cu 2 0) 


(Cu) 


(d-glucose) 


10 


8.9 


4.0 


45 


40.0 


19.1 


11 


9.8 


4.5 


46 


40.9 


19.6 


12 


10.7 


4.9 


47 


41.7 


20.0 


13 


11.5 


5.3 


48 


42.6 


20.4 


14 


12.4 


5.7 


49 


43.5 


20.9 


15 


13.3 


6.2 


50 


44.4 


21.3 


16 


14.2 


6.6 


51 


45.3 


21.7 


17 


15.1 


7.0 


52 


46.2 


22.2 


18 


16.0 


7.5 


53 


47.1 


22.6 


19 


16.9 


7.9 


54 


48.0 


23.0 


20 


17.8 


8.3 


55 


48.9 


23.5 


21 


18.7 


8.7 


56 


49.7 


23.9 


22 


19.5 


9.2 


57 


50.6 


24.3 


23 


20.4 


9.6 


58 


51.5 


24.8 


24 


21.3 


10.0 


59 


52.4 


25.2 


25 


22.2 


10.5 


60 


53.3 


25.6 


26 


23.1 


10.9 


61 


54.2 


26.1 


27 


24.0 


11.3 


62 


55.1 


26.5 


28 


24.9 


11.8 


63 


56.0 


27.0 


29 


25.8 


12.2 


64 


56.8 


27.4 


30 


26.6 


12.6 


65 


57.7 


27.8 


31 


27.5 


13.1 


66 


58.6 


28.3 


32 


28.4 


13.5 


67 


59.5 


28.7 


33 


29.3 


13.9 


68 


60.4 


29.2 


34 


30.2 


14.3 


69 


61.3 


29.6 


35 


31.1 


14.8 


70 


62.2 


30.0 


36 


32.0 


15.2 


71 


63.1 


30.5 


37 


32.9 


15.6 


72 


64.0 


30.9 


38 


33.8 


16.1 


73 


64.8 


31.4 


39 


34.6 


16.5 


74 


65.7 


31.8 


40 


35.5 


16.9 


75 


l 66.6 


32.2 


41 


36.4 


17.4 


76 


67.5 


32.7 


42 


37.3 


17.8 


77 


I 68.4 


33.1 


43 


38.2 


18.2 


78 


69.3 


33.6 


44 


39.1 


18.7 


79 


1 70.2 


34.0 



628 



PRACTICAL TANNING 



Cuprous 






Cuprous 






oxide 


Copper 


Dextrose 


oxide 


Copper 


Dextrose 


(Cu 2 0) 


(Cu) 


(d-glucose) 


(Cu 2 0) 


(Cu) 


(d-glucose) 


80 


71.1 


34.4 


115 


102.2 


. 50.0 


81 


71.9 


34.9 


116 


103.0 


50.5 


82 


72.8 


35.3 


117 


103.9 


50.9 


83 


73.7 


35.8 


118 


104.8 


51.4 


84 


74.6 


36.2 


119 


105.7 


51.8 


85 


75.5 


36.7 


120 


106.6 


52.3 


86 - 


76.4 


37.1 


121 


107.5 


52.7 


87 


77.3 


37.5 


122 


108.4 


53.2 


88 


78.2 


38.0 


123 


109.3 


53.6 


. 89 


79.1 


38.4 


124 


110.1 


54.1 


90 


79.9 


38.9 


125 


111.0 


54.5 


91 


80.8 


39.3 


126 


111.9 


55.0 


92 


81.7 


39.8 


127 


112.8 


55.4 


93 


82.6 


40.2 


128 


113.7 


55.9 


94 


83.5 


40.6 


129 


114.6 


56.3 


95 


84.4 


41.1 


130 


115.5 


56.8 


96 


85.3 


41.5 


131 


116.4 


57.2 


97 


86.2 


42.0 


132 


117.3 


57.7 


98 


87.1 


42.4 


133 


118.1 


58.1 


99 


87.9 


42.9 


134 


119.0 


58.6 


100 


88.8 


43.3 


135 


119.9 


59.0 


101 


89.7 


43.8 


136 


120.8 


59.5 


102 


90.6 


44.2 


137 


121.7 


60.0 


103 


91.5 


44.7 


138 


122.6 


60.4 


104 


92.4 


45.1 


139 


123.5 


60.9 


105 


93.3 


45.5 


140 


124.4 


61.3 


106 


94.2 


46.0 


141 


125.2 


61.8 


107 


95.0 


46.4 


142 


126.1 


62.2 


108 


95.9 


46.9 


143 


127.0 


62.7 


109 


96.8 


47.3 


144 


127.9 


63.1 


110 


97.7 


47.8 


145 


128.8 


63.6 


111 


98.6 


48.2 


146 


129.7 


64.0 


112 


99.5 


48.7 


147 


130.6 


64.5 


113 


100.4 


49.1 


148 


131.5 


65.0 


114 


101.3 


49.6 


149 


132.4 


65.4 



ANALYTICAL METHODS 



629 



Cuprous 
oxide 
(Cu 2 0) 

150 
151 
152 
153 
154 

155 
156 
157 
158 
159 

160 
161 
162 
163 
164 

165 
166 
167 
168 
169 

170 
171 
172 
173 
174 

175 
176 
177 

178 
179 



Copper 
(Cu) 

133.2 
134.1 
135.0 
135.9 
136.8 

137.7 
138.6 
139.5 
140.3 
141.2 

142.1 
143.0 
143.9 
144.8 
145.7 

146.6 
147.5 
148.3 
149.2 
150.1 

151.0 
151.9 
152.8 
153.7 
154.6 

155.5 
156.3 
157.2 
158.1 
159.0 



180 


159.9 


181 


160.8 


182 


161.7 


183 


162.6 


184 


163.4 



Dextrose 
(d-glucose) 

65.9 
66.3 
66.8 
67.2 

67.7 

68.2 
68.6 
69.1 
69.5 
70.0 

70.4 
70.9 
71.4 
71.8 
72.3 

72.8 
73.2 
73.7 
74.1 
74.6 

75.1 
75.5 
76.0 
76.4 
76.9 



77.4 
77.8 
78.3 
78.8 
79.2 

79.7 
80.1 
80.6 
81.1 
81.5 



Cuprous 
oxide 
(Cu 2 0) 



185 
186 

187 
188 
189 

190 
191 
192 
193 
194 

195 
196 
197 
198 
199 

200 
201 
202 
203 
204 

205 
206 
207 
208 
209 

210 
211 
212 
213 
214 

215 
216 
217 
218 
219 



Copper 
(Cu) 



Dextrose 
(d-glucose) 



164.3 
165.2 
166.1 
167.0 
167.9 

168.8 
169.7 
170.5 
171.4 
172.3 

173.2 
174.1 
175.0 
175.9 

176.8 

177.7 
178.5 
179.4 
180.3 
181.2 

182.1 
183.0 
183.9 

184.8 
185.6 

186.5 
187.4 
188.3 
189.2 
190.1 

191.0 

191.9 
192.8 
193.6 
194.5 



82.0 
82.5 
82.9 
83.4 
83.9 

84.3 

84.8 
85.3 

85.7 
86.2 

86.7 
87.1 
87.6 
88.1 
88.5 

89.0 
89.5 
89.9 
90.4 
90.9 

91.4 
91.8 
92.3 
92.8 
93.2 

93.7 
94.2 
94.6 
95.1 
95.6 

96.1 
96.5 
97.0 
97.5 
98.0 



630 



PRACTICAL TANNING 



Cuprous 
oxide 
(Cu 2 0) 


Copper 
(Cu) 


Dextrose 
(ti-glucose) 


Cuprous 
oxide 
(Cu 2 0) 


Copper 

(Cu) 


Dextrose 
(d-glucose) 


220 


195.4 


98.4 


255 


226.5 


115.2 


221 


196.3 


98.9 


• 256 


227.4 


115.7 


222 


197.2 


99.4 


257 


228.3 


116.1 


223 


198.1 


99.9 


258 


229.2 


116.6 


224 


199.0 


100.3 


259 


230.1 


117.1 


225 


199.9 


100.8 


260 


231.0 


117.6 


226 


200.7 


101.3 


261 


231.8 


118.1 


227 


201.6 


101.8 


262 


232.7 


118.6 


228 


202.5 


102.2 


263 


233.6 


119.0 


229 


203.4 


102.7 


264 


234.5 


119.5 


230 


204.3 


103.2 


265 


235.4 


120.0 


231 


205.2 


103.7 


266 


236.3 


120.5 


232 


206.1 


104.1 


267 


237.2 


121.0 


233 


207.0 


104.6 


268 


238.1 


121.5 


234 


207.9 


105.1 


269 


238.9 


122.0 


235 


208.7 


105.6 


270 


239.8 


122.5 


236 


209.6 


106.0 


271 


240.7 


122.9 


237 


210.5 


106.5 


272 


241.6 


123.4 


238 


211.4 


107.0 


273 


242.5 


123.9 


239 


212.3 


107.5 


274 


243.4 


124.4 


240 


213.2 


108.0 


275 


244.3 


124.9 


241 


214.1 


108.4 


276 


245.2 


125.4 


242 


215.0 


108.9 


277 


246.1 


125.9 


243 


215.8 


109.4 


278 


246.9 


126.4 


244 


216.7 


109.9 


279 


247.8 


126.9 


245 


217.6 


110.4 


280 


248.7 


127.3 


246 


218.5 


110.8 


281 


249.6 


127.8 


247 


219.4 


111.3 


282 


250.5 


128.3 


248 


220.2 


111.8 


283 


251.4 


128.8 


249 


221.2 


112.3 


284 


252.3 


129.3 


250 


222.1 


112.8 


285 


253.2 


129.8 


251 


223.0 


113.2 


286 


254.0 


130.3 


252 


223.8 


113.7 


287 


254.9 


130.8 


253 


224.7 


114.2 


288 


255.8 


131.3 


254 


225.6 


114.7 


289 


256.7 


131.8 



ANALYTICAL METHODS 



031 



Cuprous 






Cuprous 






oxide 


Copper 


Dextrose 


oxide 


Copper 


Dextrose 


(Cu 2 0) 


(Cu) 


(rf-glucose) 


(Cu 2 0) 


(Cu) 


(d-glucose) 


290 


257.6 


132.3 


325 


288.7 


149.7 


291 


258.5 


132.7 


326 


289.6 


150.2 


292 


259.4 


133.2 


327 


290.5 


150.7 


293 


260.3 


133.7 


328 


291.4 


151.2 


294 


261.2 


134.2 


329 


292.2 


151.7 


295 


262.0 


134.7 


330 


293.1 


152.2 


296 


262.9 


135.2 


331 


294.0 


152.7 


297 


263.8 


135.7 


332 


294.9 


153.2 


298 


264.7 


136.2 


333 


295.8 


153.7 


299 


265.6 


136.7 


334 


296.7 


154.2 


300 


266.5 


137.2 


335 


297.6 


154.7 


301 


267.4 


137.7 


336 


298.5 


155.2 


302 


268.3 


138.2 


337 


299.3 


155.8 


303 


269.1 


138.7 


338 


300.2 


156.3 


304 


270.0 


139.2 


339 


301.1 


156.8 


305 


270.9 


139.7 


340 


302.0 


157.3 


306 


271.8 


140.2 


341 


302.9 


157.8 


307 


272.7 


140.7 


342 


303.8 


158.3 


308 


273.6 


141.2 


343 


304.7 


158.8 


309 


274.5 


141.7 


344 


305.6 


159.3 


310 


275.4 


142.2 


345 


306.5 


159.8 


311 


276.3 


142.7 


346 


307.3 


160.3 


312 


277.1 


143.2 


347 


308.2 


160.8 


313 


278.0 


143.7 


348 


309.1 


161.4 


314 


278.9 


144.2 


349 


310.0 


161.9 


315 


* 279.8 


144.7 


350 


310.9 


162.4 


316 


280.7 


145.2 


351 


311.8 


162.9 


317 


281.6 


145.7 


352 


312.7 


163.4 


318 


282.5 


146.2 


353 


313.6 


163.9 


319 


283.4 


146.7 


354 


314.4 


164.4 


320 


284.2 


147.2 


355 


315.3 


164.9 


321 


285.1 


147.7 


356 


316.2 


165.4 


322 


286.0 


148.2 


357 


317.1 


166.0 


323 


286.9 


148.7 


358 


318.0 


166.5 


324 


287.8 


149.2 


359 

1 


318.9 


167.0 



632 



PRACTICAL TANNING 



Cuprous 






Cuprous 






oxide 


Copper 


Dextrose 


oxide 


Copper 


Dextrose 


(Cu 2 0) 


(Cu) 


(d-glucose) 


(Cu 2 0) 


(Cu) 


(d-glucose) 


360 


319.8 


167.5 


395 


350.9 


185.7 


361 


320.7 


168.0 


396 


351.8 


186.2 


362 


321.6 


168.5 


397 


352.6 


186.8 


363 


322.4 


169.0 


398 


353.5 


187.3 


364 


323.3 


169.6 


399 


354.4 


187.8 


365 


324.2 


170.1 


400 


355.3 


188.4 


366 


325.1 


170.6 


401 


356.2 


188.9 


367 


326.0 


171.1 


402 


357.1 


189.4 


368 


326.9 


171.6 


403 


358.0 


189.9 


369 


327.8 


172.1 


404 


358.9 


190.5 


370 


328.7 


172.7 


405 


359.7 


191.0 


371 


329.5 


173.2 


406 


360.6 


191.5 


372 


330.4 


173.7 


407 


361.5 


192.1 


373 


331.3 


174.2 


408 


362.4 


192.6 


374 


332.2 


174.7 


409 


363.3 


193.1 


375 


333.1 


175.3 


410 


364.2 


193.7 


376 


334.0 


175.8 


411 


365.1 


194.2 


377 


334.9 


176.3 


412 


366.0 


194.7 


378 


335.8 


176.8 


413 


366.9 


195.2 


379 


336.7 


177.3 


414 


367.7 


195.8 


380 


337.5 


177.9 


415 


368.6 


196.3 


381 


338.4 


178.4 


416 


369.5 


196.8 


382 


339.3 


178.9 


417 


370.4 


197.4 


383 


340.2 


179.4 


418 


371.3 


197.9 


384 


341.1 


180.0 


419 


372.2 


198.4 


385 


342.0 


180.5 


420 


373.1 ' 


199.0 


386 


342.9 


181.0 


421 


374.0 


199.5 


387 


343.8 


181.5 


422 


374.8 


200.1 


388 


344.6 


182.0 


423 


375.7 


200.6 


389 


345.5 


182.6 


424 


376.6 


201.1 


390 


346.4 


183.1 


425 


377.5 


201.7 


391 


347.3 


183.6 


426 


378.4 


202.2 


392 


348.2 


184.1 


427 


379.3 


202.8 


393 


349.1 


184.7 


428 


380.2 


203.3 


394 


350.0 


185.2 


429 


381.1 


203.8 



ANALYTICAL METHODS 



633 



Cuprous 






Cuprous 






oxide 


Copper 


Dextrose 


oxide 


Copper 


Dextrose 


(Cu 2 0) 


(Cu) 


(d-glucose ) 


(Cu 2 0) 


(Cu) 


(d-glucose) 


430 


382.0 


204.4 


460 


408.6 


220.7 


431 


382.8 


204.9 


461 


409.5 


221.3 


432 


383.7 


205.5 


462 


410.4 


221.8 


433 


384.6 


206.0 


463 


411.3 


222.4 


434 


385.5 


206.5 


464 


412.2 


222.9 


435 


386.4 


207.1 


465 


413.0 


223.5 


436 


387.3 


207.6 


466 


413.9 


224.0 


437 


388.2 


208.2 


467 


414.8 


224.6 


438 


389.1 


208.7 


468 


415.7 


225.1 


439 


390.0 


209.2 


469 


416.6 


225.7 


440 


390.8 


209.8 


470 


417.5 


226.2 


441 


391.7 


210.3 


471 


418.4 


226.8 


442 


392.6 


210.9 


472 


419.3 


227.4 


443 


393.5 


211.4 


473 


420.2 


227.9 


444 


394.4 


212.0 


474 


421.0 


228.5 


445 


395.3 


212.5 


475 


421.9 


229.0 


446 


396.2 


213.1 


476 


422.8 


229.6 


447 


397.1 


213.6 


477 


423.7 


230.1 


448 


397.9 


214.1 


478 


424.6 


230.7 


449 


398.8 


214.7 


479 


425.5 


231.3 


450 


399.7 


215.2 


480 


426.4 


231.8 


451 


400.6 


215.8 


481 


427.3 


232.4 


452 


401.5 


216.3 


482 


428.1 


232.9 


453 


402.4 


216.9 


483 


429.0 


233.5 


454 


403.3 


217.4 


484 


429.9 


234.1 


455 


404.2 


218.0 


485 


430.8 


234.6 


456 


405.1 


218.5 


486 


431.7 


235.2 


457 


405.9 


219.1 


487 


432.6 


235.7 


458 


406.8 


219.6 


488 


433.5 


236.3 


459 


407.7 


220.2 


489 


434.4 


236.9 








490 


435.3 


237.4 



634 PRACTICAL TANNING 

(7) Nitrogen. — Gunning modification of the Kjeldahl 
method, A. O. A. C. Bulletin, No. 107 (1907). 

Reagents 

Standard acid solutions. — Hydrochloric or sulphuric acid, 
the absolute strength of which has been accurately deter- 
mined : For ordinary work half-normal acid is recommended. 
For work in determining very small amounts of nitrogen, 
tenth-normal is recommended. In titrating mineral acid 
against hydroxide solution use cochineal as indicator. 

Standard alkali solution. — The strength of this solution 
relative to the acid must be accurately determined; tenth- 
normal solution is recommended. 

Sulphuric acid. — The sulphuric acid used should have a 
specific gravity of 1.84 and be free from nitrates, also from 
ammonium sulphate. 

Sodium hydroxide solution. — A saturated solution of so- 
dium hydroxide free from nitrates. 

Potassium sulphate. — This reagent should be pulverized be- 
fore using. 

Indicator. — A solution of cochineal is prepared by digest- 
ing and frequently agitating 3 grams of pulverized cochineal 
in a mixture of 50 cc. of strong alcohol and 200 cc. of dis- 
tilled water for a day or two at ordinary temperature; the 
filtered solution is employed as indicator. 

Determination 

Place 0.7 gram of leather in a digestion flask. Add 10 
grams of powdered potassium sulphate and from 15 to 25 cc. 
(ordinarily about 20 cc.) of concentrated sulphuric acid. 
Place the flask in an inclined position and heat below the 
boiling point of the acid from 5 to 15 minutes, or until froth- 
ing has ceased (a small piece of paraffin may be added to pre- 
vent extreme foaming). 

Then raise the heat and boil briskly until the liquid has 



ANALYTICAL METHODS 635 

become quite clear and nearly colorless (the digestion should 
take from 4 to 5 hours). 

After cooling, dilute with about 200 cc. of water. Next 
add 50 cc. of soda solution, or sufficient to make the reaction 
strongly alkaline, pouring it down the side of the flask so 
that it does not mix at once with the acid solution. Connect 
the flask with the condenser, mix the contents by shaking, 
and distil until all ammonia has passed over into the stand- 
ard acid. The first 150 cc. will generally contain all the am- 
monia. The operation usually requires from 40 minutes to 
1^ hours. The distillate is then titrated with standard alkali. 

Previous to use, the reagents should be tested by a blank- 
experiment with sugar, which will partly reduce any nitrates 
present that, otherwise, might escape notice. 

Chrome-tanned leather. — In an ordinary analysis of 
chrome-tanned leather the sample is analyzed for fat, ash, and 
chromium. 

Fat. — About 15 grams of the leather is weighed out and 
dried at a temperature of 105° C. for 2 hours. This dry 
sample is put in a Soxhlet extractor and extracted on the water- 
bath with petroleum ether for 3 hours. Distil off the ether 
and remove the last traces by heating in the water-oven at a 
temperature of 105° C. Weigh and subtract weight of the 
empty flask to get the weight of. the fat residue. 

Percentage of fat - g^ms fat residue X 100 
weight of sample 

Free sulphur. — If there is free sulphur in the leather it can 
be determined by extracting a sample as described above, sub- 
stituting carbon disulphide for the petroleum ether, and the 
residue calculated to fat and sulphur. This fat and sulphur 
residue is now covered with fuming nitric acid and allowed 
to stand over night, thus oxidizing the S to SO4. Evaporate 
nearly to dryness in an evaporating dish, add 100 cc. water, 
boil and filter. Make the filtrate acid with hydrochloric acid 
and precipitate the sulphuric acid with barium chloride solu- 
tion in the usual way. 



636 PRACTICAL TANNING 

weight BaS0 4 X 0.137 X 100 

Percentage or b = r-rr — j ; " 

weight of sample 

Percentage of fat = percentage of fat + S — . percentage 
of S. 

Ash. — A 5-gram sample is weighed into a platinum dish 

and ignited, gently at first, then at high heat to constant 

weight. 

. , weight of residue X 100 

Percentage of ash = ^j— — t i 

& weight ol sample 

Chromium. — The ash from the above determination is 
transferred to an iron crucible and intimately mixed with 
about five times its weight of sodium peroxide. Heat gently 
at first then fuse well for about 10 minutes. (Warning: 
Keep face away from fusion mixture. ) Cool, place in a small 
casserole, cover with water and boil for about 20 minutes. 
Cool, filter into a 500 cc. graduated flask. Wash the paper 
well, allowing the washings to run into a flask. Pipette off 
100 cc. into a 400 cc. beaker and add 25 cc. of hydrochloric 
acid, some 10 per cent potassium iodine solution and titrate 
with N/10 hypo in the usual way, using starch as an indicator. 

, „ ' cc. N/10 Na 2 S 2 3 X 0.00253 X 5 X 100 

Percentage of Cr 2 3 = . ,. , -, 

fe weight of sample 

( Note : — In place of the sodium peroxide the ash may be 
heated with four times its weight of equal parts of magnesium 
oxide and sodium carbonate, stirring frequently with a plat- 
inum wire, or fused with about five times its weight of a mix- 
ture consisting of equal parts of sodium and potassium car- 
bonate with a small quantity of potassium nitrate.) 

If the leather contains a large amount of grease, the G*203 
is best calculated to the weight of leather obtained after the 
fat is extracted. A well-tanned chrome leather should con- 
tain at least 2.8 per cent of Cr2C>3. 

Complete analysis. — While the above determinations are 
usually sufficient, additional determinations are sometimes 
needed. The following is a scheme given by Procter for a 
complete analysis, using four different samples : 



ANALYTICAL METHODS 637 

A. (1) Water (7) Tannins 

(2) Ash (8) Sugar 

(3) Chromium (9) Sulphates 

(4) Alumina (10) Chlorides 

B. (5) Fat (11) Barium 
(6) Sulphur (12) Lead 

Water solubles C. (15) Alkaline salts 

Water insolubles D. (16) Hide substance 

A. A 5-gram sample is weighed out and the following 
determinations made : 

Water. — The percentage of water is determined by heating 
the sample to constant weight at a temperature of 105° C. 
loss in weight X 100 



Percentage of H 2 = 
Ash. — The above c 
Percentage of ash = 



5 
Ash. — The above dry sample is ignited to constant weight, 
weight of residue X 100 



5 

Chromium and aluminum. — The ash is fused as described 
under chromium determination. The fused mass is then 
boiled with water and filtered into a 250 cc. graduated flask. 
The residue on the filter-paper is well washed with hot water, 
and the washings run into the flask. The solution is cooled, 
made up to the mark, and 50 cc. pipetted off and analyzed 
iodometrically for chromium as described above. Calculate 
to O2O3. 

For aluminum, 50 cc. of above solution is pipetted into a 
250 cc. beaker, the solution made strongly acid with hydro- 
chloric acid. Alcohol is then added and boiled to reduce the 
chromium to the three-bonded condition. The solution is 
now made alkaline with ammonium hydroxide and boiled until 
the odor of ammonia is very faint. Filter hot, wash well with 
hot water, ignite, weigh, and calculate as per cent of O2O3 -j- 
A12O3. The percentage of AI2O3 is found by subtracting 
from the percentage of O2O3 + AI2O3 the percentage of 
Cr2C>3 found iodometrically. 

B. The 20-gram sample is weighed out, dried at 105° C, 
and the following determination made : 

Fat and sulphur are determined from the above sample as 
previously outlined. 



638 PRACTICAL TANNING 

Water solubles. — The 20-gram sample from which the fat 
and sulphur have been extracted is heated to 105° C. for 2 
hours to drive off all petroleum ether or carbon disulphide. 
The water solubles are dissolved from this dried sample in 
the manner described under vegetable-tanned leather, 500 cc. 
of the extract being collected. Small samples of this extract 
are then tested for the following: 

Tannins. — Vegetable tannins are tested for with iron alum 
(getting blue or green precipitate) and if present are deter- 
mined quantitatively as outlined under vegetable tannin 
analysis. 

Sugar. — A small sample of water-soluble material is treated 
with basic lead acetate to precipitate the tannin, and the excess 
of lead precipitated as PbC2C>4. The solution is then boiled 
with dilute hydrochloric acid, neutralized with sodium car- 
bonate and boiled with Fehling solution. The presence of 
sugar is shown by the reduction of copper sulphate to red 
C112O. If sugar is found to be present it can be determined 
quantitatively as outlined under vegetable-tanned leather. 

Sulphates. — A small sample boiled with hydrochloric acid 
and barium chloride gives a white precipitate if sulphates are 
present. Determine quantitatively in the usual manner. 

Chlorides. — A white precipitate with nitric acid and silver 
nitrate shows the presence of chlorides. It should be deter- 
mined quantitatively in the usual manner, filtering on a Gooch, 
washing, drying, and weighing as AgCl. 

Barium. — In the absence of sulphates, barium may be pres- 
ent. It can be tested for by adding a little sulphuric acid to 
a part of the solution. A white precipitate, insoluble in KOH, 
proves barium. A white precipitate soluble in KOH or 
NH4C2H3O2 indicates lead. 

Water insolubles: Sulphates. — After extraction with hot 
water, the leather is soaked in 10 per cent sodium carbonate 
solution, ashed, and fused. The fused mass is boiled with 
water, filtered, washed, and the sulphates in the filtrate deter- 
mined by precipitating with barium chloride. 

Barium and lead. — The fused ash insoluble in water is 



ANALYTICAL METHODS 639 

boiled with dilute hydrochloric acid and filtered. The barium 
and lead are precipitated from the filtrate with sulphuric acid. 
The BaS0 4 and PbS0 4 are weighed together. The PbS0 4 
is then dissolved with NH4C2H3O2, the BaS0 4 weighed up, 
and the PbS0 4 obtained by difference. 

C. Alkaline salts. — Fifteen grams of leather is extracted 
with carbon disulphide, and the excess driven off. It is then 
covered with 100 cc. of fuming nitric acid and allowed to 
stand over night. It is finally evaporated to dryness, dissolved 
in hot water, filtered, and made up to 250 cc. From this 
solution total soluble sulphates and alkaline sulphates can be 
determined. 

(a) Total soluble sulphates. — 100 cc. is pipetted off, the 
solution acidified with hydrochloric acid, and the sulphates 
precipitated with barium chloride in the usual manner. 

(b) Alkaline sulphates. — 100 cc. is pipetted off, evaporated 
to dryness, and ignited to remove organic matter. The resi- 
due is boiled with hydrochloric acid, evaporated to a small 
volume and traces of chromium removed by boiling with am- 
monia. Filter, add a few drops of concentrated sulphuric 
acid to the filtrate, evaporate, ignite at not too high a tempera- 
ture, and weigh as alkaline sulphates. 

D. Hide substance. — This is determined by the Kjeldahl 
method, as outlined under vegetable-tanned leather. 

PROVISIONAL METHOD FOR THE ANALYSIS OF CHROME 

LEATHER 

Chrome determination. — (a) Ash 3 grams of leather. Mix 
the ash well with 4 grams of a mixture of equal parts of so- 
dium carbonate, potassium carbonate, and powdered borax 
glass and fuse for 30 minutes. Dissolve the cooled fusion in 
hot water with enough hydrochloric acid to make the solution 
acid. Filter, and if there is any residue on the paper, ash it 
and treat the ash with 1 gram of the fusion mixture in the 
same manner as is the original ash, adding the solution to the 
first, and make up to 500 cc. To 100 cc. of this solution in 



640 PRACTICAL TANNING 

an Erlenmeyer flask add 5 cc. hydrochloric acid, and determine 
CraC>3 as above under the analysis of one-bath chrome liquors, 
(b) If it is not desired to determine Fe or Al, the ash of 
3 grams of leather may be transferred to an iron crucible, 
mixed with '3 grams of sodium peroxide and fused 10 min- 
utes. Place the cooled crucible in 300 cc. water in a casserole 
and boil 20 minutes. Wash into a 500 cc. flask, cool, and 
make up to the mark. Filter through a dry filter. Place 100 
cc. of filtrate in an Erlenmeyer flask, neutralize with hydro- 
chloric acid, add 5 cc. excess and proceed as in (a). 

PROVISIONAL METHOD FOR SULPHONATED OILS 

Moisture. — Weigh between 30 and 40 grams (depending on 
amount of water present) into a flask of 250 to 300 cc. ca- 
pacity and add 75 cc. water-saturated xylol, prepared by heat- 
ing a mixture of water and xylol with frequent shaking and 
subsequently removing the water in a separatory funnel. Con- 
nect to a Liebig condenser and place the flask in a bath of 
paraffin or a heavy lubricating oil. Distil moderately until 
the distillate becomes clear. Collect the distillate in a tube 
graduated to 1/10 cc. and wash the condenser with a stream 
of xylol from a wash-bottle. Place the graduated tube in hot 
water and when the distillate is clear, cool. The percentage 
of moisture is obtained by dividing the volume of water in 
the distillate by the weight of oil taken. 

(Note: — For the graduated tube Eimer and Amend's No. 
3812 is recommended.) 

Ash. — Weigh any convenient quantity into a dish or cruci- 
ble. Ignite gently, allowing the oil to burn until all carbon 
is consumed. 

Non-sap onifiabie. — Weigh approximately 10 grams of oil 
into an 8-oz. Erlenmeyer flask and add 5 cc. aqueous KOH 
solution (50 grams KOH in water and dilute to 100 cc), 45 
cc. ethyl-alcohol, and a few glass beads. Boil one hour with 
reflux condenser. Add 100 cc. water and cool. Transfer 
to separatory funnel and shake at least three times with petrol- 



ANALYTICAL METHODS 641 

eum ether (B. P. 40 to 75° C. ) using 50 cc. each time. Wash 
ether layer at least three times with 50 cc. water containing" 
10 cc. ethyl-alcohol. Use alcohol to break emulsion. Evaporate 
ether extract in tared vessel, cool and weigh. 

(Note: — If the contents of the flask bump violently during 
saponification add 25 cc. petroleum ether, and proceed. 

Combined SO3. — (a) Weigh approximately 4 grams into 
an Erlenmeyer flask and boil for 40 minutes with 30 cc. HO 
(1 : 5). Shake frequently. Cool, transfer to separatory fun- 
nel, and shake out with petroleum ether. Draw off aqueous 
layer and wash ethereal layer with water. Combine wash- 
ings with main aqueous portion and determine the sulphuric 
acid as barium sulphate. From the amount thus found, the 
quantity as determined in (b) is subtracted and the difference 
calculated as SO3. 

(b) Dissolve 4 grams in ether and shake out several times 
with 25 cc. of concentrated brine free from sulphates. Com- 
bine the washings, dilute, filter, and determine the sulphuric 
acid as barium sulphate. 

Total fatty oil. — The total fatty oil shall be the difference 
between 100 per cent and the sum of moisture, ash and non- 
saponifiable. 

(Note: — The results obtained by these methods shall be 
reported only to one decimal place.) 

PROVISIONAL METHOD FOR ANALYSIS OF MOELLONS 

Moisture. — Weigh accurately 3 grams of the sample in a 
wide platinum dish, and heat with a low flame until the mois- 
ture is all driven off. This point can be determined by the 
appearance of smoke, and a slight crackling sound. Place 
the dish in a desiccator, cool and weigh. 

Ash. — Ash the moellon remaining in the dish after the 
moisture determination in the usual manner, cool, and weigh. 

Unsaponifiable. — Weigh accurately in a 300 cc. flask, 5 
grams of the moellon, add 2.5 grams of caustic potash dis- 
solved in a little water (or 5 cc. of a 50 per cent KOH solu- 



642 PRACTICAL* TANNING 

tion), and 25 cc. of 95 per cent alcohol, boil with reflux con- 
denser for 1 hour, shaking occasionally. Glass beads may be 
used to prevent bumping. Add 50 cc. of hot water, cool, 
transfer to a separatory funnel, and extract three times, using 
40 cc. of petroleum ether for each extraction. A little alco- 
hol may be added to break persistent emulsions. Wash the 
combined ether solutions three times with a moisture of 30 
cc. of water and 10 cc. of alcohol, transfer to a tared dish, 
evaporate to dryness, cool and weigh. Excessive drying must 
be avoided. 

Oxidized fatty acids. — Boil the soap solution remaining 
from the unsaponifiable determination until all the alcohol is 
expelled, then dissolve in hot water, transfer to a separatory 
funnel, rinse the beaker thoroughly into the funnel, bringing 
the volume to approximately 300 cc, and immediately add a 
slight excess of concentrated HC1 (about 25 per cent more 
than sufficient to neutralize the total alkali). Rotate the con- 
tents of the flask vigorously, cool and shake out with petro- 
leum ether. Run off the aqueous layer, and pour off the 
ether layer, avoiding any loss of oxidized fatty acids. Wash 
these acids twice with small quantities of petroleum ether and 
hot water; dissolve in warm 95 per cent alcohol, filter if 
necessary, transfer to a tared dish, and place in an ordinary 
evaporator and dryer for 16 hours, then cool and weigh. 
The entire operation should be conducted without delay. 

Free fatty acids.— Weigh out 1 gram moellon, dissolve in 
mixture of 20 cc. of alcohol and 20 cc. of sulphuric ether, 
which has been neutralized to phenolphthalein, and titrate with 
N/10 NaOH, using phenolphthalein as indicator. Test for 
mineral acids or alkalies (by adding methyl-orange to the 
water emulsion of the moellon), and if present, make the 
necessary correction. 

PROVISIONAL METHOD FOR ANALYSIS OF HARD 
GREASES 

Titer test. — Saponify 75 grams of fat in a metal dish with 
60 cc. of 30 per cent sodium hydroxide (36° Be.) and 75 cc. 



ANALYTICAL METHODS 643 

of 95 per cent by volume alcohol or 120 cc. of water. Evap- 
orate to dryness over a very low flame or over an iron or 
asbestos plate, stirring constantly to prevent scorching. Dis- 
solve the dry soap in a liter of boiling water, and if alcohol 
has been used, boil for 40 minutes in order to remove it, add- 
ing sufficient water to replace that lost in boiling. Add 100 
cc. of 30 per cent sulphuric acid (25° Be.) to free the fatty 
acids and boil until they form a clear, transparent layer. Wash 
with boiling water until free from sulphuric acid, collect in 
a small beaker, and place on the steam bath until the water 
has settled and the fatty acids are clear; then decant into a 
dry beaker, filter, using hot water funnel, and dry 20 minutes 
at 100° C. When dried, cool the fatty acids to 15 or 20° C. 
above the expected titer and transfer to the titer tube, which 
is 25 mm. in diameter and 100 mm. in length ( 1 by 4 inches) 
and made of glass about 1 mm. thick. Place in a 16-ounce salt 
mouth bottle of clear glass, about 70 mm. in diameter and 150 
mm. high (2.8 by 6 inches), fit it with a cork, which is perfor- 
ated so as to hold the tube rigidly when in position. Suspend 
the thermometer, graduated to 0.10° C, so that it can be used 
as a stirrer, and stir the mass slowly until the mercury re- 
mains stationary for 30 seconds. Then allow the thermometer 
to hang quietly, with the bulb in the center of the mass, and 
observe the rise of the mercury. The highest point to which 
it rises is recorded as the titer of the fatty acids. 

Test the fatty acids for complete saponification as follows : 

Place 3 cc. in a test-tube and add 15 cc. of alcohol (95 
per cent by volume). Bring the mixture to a boil and add 
an equal volume of ammonium hydroxide (0.96 sp. gr.). A 
clear solution should result, turbidity indicating unsaponified 
fat. The titer must be made at about 20° C. for all fats 
having a titer above 30° C, and at 10° C. below the titer for 
all other fats. 

Unsaponifiable. — Same as for unsaponifiable in moellons. 

Free fatty acids. — Same as for free fatty acids in moellons. 



644 



PRACTICAL TANNING 



PROVISIONAL METHOD FOR ANALYSIS OF LACTIC ACID 

Free sulphuric acid. — Dissolve 50 grams of the sample in 
200 cc. of alcohol, which should be neutral, and of at least 
95 per cent strength. Heat to 60° C, cover, and let stand 
over night in a warm place. Filter off precipitated material 
and wash with alcohol. Evaporate off the alcohol, make up 
the residue to 250 cc. with water, add 5 cc. strong HC1, boil, 
add BaCb and determine BaSC>4 in the usual way. Calcu- 
late to percentage of H2SO4 on the original sample. 

Volatile acid. — Weigh out 1 gram of sample, make up to 
about 50 cc. with water, titrate with N/5 NaOH. Calcu- 
late the result to lactic acid: (1 cc. N/5 NaOH = 0.045 
gram lactic acid.) On this basis, make up a solution con- 



Table Showing the Relation of Amounts of Volatile 
Acid Found in Distillate Obtained Under Stand- 
ard Conditions to the Amounts Actually Present 
in Distilling Flask, in Milligrams. 



One Distillation 



In dis- 




In dis- 




In dis- 




In dis- 




tillate 


In flask 


tillate 


In flask 


tillate 


In flask 


tillate 


In flask 


1 


0.0 


14 


17.5 


27 


37.5 


40 


57.9 


2 


0.0 


15 


19.0 


28 


39.0 


41 


59.6 


3 


0.0 


16 


20.5 


29 


40.6 


42 


61.3 


4 


2.0 


17 


22.1 


30 


42.1 


43 


62.9 


5 


3.5 


18 


23.6 


31 


43.7 


44 


64.6 


6 


5.1 


19 


25.2 


32 


45.2 


45 


66.3 


7 


6.7 


20 


26.7 


33 


46.8 


46 


68.0 


8 


8.2 


21 


28.2 


34 


48.3 


47 


69.8 


9 


9.8 


22 


29.8 


35 


49.9 


48 


71.5 


10 


11.3 


23 


31.3 


36 


51.5 


49 


73.3 


11 


12.8 


24 


32.9 


37 


53.1 


50 


75.0 


12 


14.4 


25 


34.4 


38 


54.7 


51 


76.8 


13 


15.9 


26 


35.9 


39 


56.3 


52 


78.5 



ANALYTICAL METHODS 
Two Distillations 



645 



In dis- 




In dis- 




In dis- 




In dis- 




tillate 


In flask 


tillate 


In flask 


tillate 


In flask 


tillate 


In flask 


5 


0.0 


22 


19.2 


39 


38.9 


56 


58.6 


6 


1.0 


23 


20.4 


40 


40.0 


57 


59.8 


7 


2.0 


24 


21.5 


41 


41.1 


58 


61.1 


8 


3.0 


25 


22.7 


42 


42.3 


59 


62.3 


9 


4.0 


26 


23.9 


43 


43.4 


60 


63.5 


10 


5.0 


27 


25.0 


44 


44.6 


61 


64.7 


11 


6.2 


28 


26.2 


45 


45.7 


62 


65.9 


12 


7.4 


29 


27.3 


46 


46.8 


63 


67.2 


13 


8.6 


30 


28.5 


47 


48.0 


64 


68.4 


14 


9.8 


31 


29.7 


48 


49.2 


65 


69.6 


15 


11.0 


32 


30.8 


49 


50.3 


66 


70.8 


16 


12.1 


33 


32.0 


50 


51.5 


67 


72.0 


17 


13.4 


34 


33.1 


51 


52.7 


68 


73.3 


18 


14.5 


35 


34.3 


52 


53.9 


69 


74.5 


19 


15.7 


36 


35.4 


53 


55.0 


70 


75.7 


20 


16.9 


37 


36.6 


54 


56.2 


71 


76.9 


21 


18.1 


38 


37.7 


55 


57.4 


72 


78.1 



taining about 15 grams of acid per liter. Place 150 cc. of 
this dilution in a long-necked 300 cc. Kjeldahl flask, con- 
nected through a Kjeldahl bulb trap to a vertical spiral con- 
denser, the total height from the bottom of the flask to the 
top of the turn connecting with the condenser being between 
20 and 24 inches. Distil over 125 cc. in from 47 to 53 min- 
utes, counting from the time the first drop falls into the re- 
ceiver, which should be a graduated cylinder. Add 125 cc. 
of water to the residue in the flask and repeat. Titrate both 
distillates with N/10 NaQH and phenolphthalein and calcu- 
late results to grams of acetic acid: 1 cc. N/10 NaOH = 
0.006 gram of acetic acid. From these figures for acid found 
in distillates find actual weight of volatile acid placed in boil- 
ing flask, by means of table, and calculate this result to per- 
centage of volatile acid in the sample. 



64,6 PRACTICAL TANNING 

Free acid and anhydride. — Titrate 50 cc. of the dilution 
made up for volatile acid, in the cold, with N/5 NaOH and 
phenolphthalein to first full pink. Call this figure "first titra- 
tion." From it subtract a number of cc. of N/5 NaOH 
equivalent to the sum of volatile acid and free sulphuric acid 
present in the 50 cc. of dilution. (If the sample contains free 
oxalic or hydrochloric acid, the amount must be determined 
by appropriate methods, and further deduction made.) Cal- 
culate the remainder to lactic acid and express it as a percen- 
tage of the sample. This is the free lactic acid. After com- 
pleting the first titration, add 4 cc. excess alkali, or in the case 
of concentrated acids, 5 cc, and stand aside at room tempera- 
ture (20—25° C.) for 15 minutes. Then add 5 cc. N/5 
H2SO4, boil, and titrate back with N/5 NaOH. The amount 
of alkali used by anhydride is now found by subtraction and 
calculated to lactic acid. Express this as percentage of lactic 
acid equivalent to anhydride present in sample. 

OFFICIAL FORM FOR REPORT ON EXTRACT ANALYSIS 

ANALYSIS 



Tannin Total solids 

Non-tannins Soluble solids . . 

Insolubles Ash 

Water Specific gravity 

Total Twaddell 



Analyzed by the official f Slowly \- 
method of the A.L.C.A. 1 Rapidly J 

Sulphuric acid in leather: Procter and Searle method. — 
This method is rapid, fairly accurate, and probably more used 
than any other method. 

A 3-gram sample of leather is soaked with 25 cc. of N/10 
sodium carbonate and evaporated to dryness on a water-bath. 
The residue is charred, pulverized, boiled out with water, and 
filtered through a quantitative filter-paper. The residue is 
ignited, treated with 25 cc. of N/10 hydrochloric acid and 
added to the above filtrate. This combined solution is now 



ANALYTICAL METHODS 647 

titrated with N/10 NaOH, using methyl-orange as an indi- 
cator. The amount of acid found is calculated to H2SO4. 

x tt or, cc - N A° Na0H X 0.0049 X 100 

Percentage of H 2 S0 4 = — 7— — -. : 

weight of sample 

Balland and Maljean method. — A 2-gram sample of leather 
is weighed out and ashed. The ash is boiled out with water, 
filtered, the sulphates in the filtrate determined by precipita- 
tion with BaCb in the usual manner, and calculated to per- 
centage of H2SO4. This represents the mineral sulphates in 
the sample. 

A second sample is weighed out, soaked with an excess of 
10 per cent Na2COs solution, dried, ashed, boiled with water, 
and the sulphates precipitated, as above. This gives a measure 
of the free sulphuric acid plus the mineral sulphates in the 
leather. Calculate the sulphates in each case. The H0SO4 
in the second example minus the H2SO4 in the first sample 
equals free H2SO4 in leather. 

Jean's method. — A sample of leather is extracted in Soxh- 
let with absolute alcohol. This dissolves the free H2SO4, 
but not the mineral sulphates. Sodium carbonate should be 
placed in the extraction flask to neutralize the H2SO4. The 
alcohol is distilled off, the Na2SC>4 is precipitated as BaSC>4 
and calculated to H2SO4. 

Soap analysis. — The sample should be finely shaved and 
put into a well-stoppered bottle. If the sample comes in small 
cakes, cross sections should be taken through the middle. In 
any case, a sample representative of the whole should be taken. 

Water. — Five grams of the sample are accurately weighed 
into a platinum dish containing a small glass rod, and heated 
carefully on a sand-bath. The soap should be constantly 
stirred with the rod to prevent burning and ensure even heat- 
ing. As soon as no moisture gathers, on a watch-glass placed 
over the dish it may be removed to a desiccator, cooled, and 
weighed. After re-heating, it is again weighed and the process 
repeated until constant weight is obtained. 

Fatty acids. — A 5 or 10-gram sample is dissolved in hot 



648 PRACTICAL TANNING 

water and washed into a separatory funnel. The soap is de- 
composed with a known quantity of standard hydrochloric 
acid, and the fatty acids thus liberated are dissolved in pe- 
troleum ether. The mixture should be well shaken to ensure 
a perfect separation. The aqueous layer is drawn into a flask, 
and the petroleum ether layer well washed with small portions 
of water. The wash water is added to the drawn-off portion. 
The petroleum ether solution is run into a tared dish, and 
evaporated to dryness and then heated to constant weight at 
100° C. 

Weight obtained X 0.97 represents fatty anhydrides. 

Total alkali. — The aqueous solution combined with the 
washings from the fatty acids is titrated with standard sodium 
hydroxide, using methyl-orange as, indicator. The difference 
between the amount of acid taken to decompose the soap and 
the back titration with sodium hydroxide represents the total 
alkali, which should be calculated as Na20. 

Insoluble in alcohol. — A 5-gram sample is dissolved in ab- 
solute alcohol. If no absolute is obtainable, 95 per cent will 
do. If there is much water in the soap, it must be dried be- 
fore dissolving. The solution is filtered through a tared filter, 
the residue washed with alcohol, dried at 100° C, and 
weighed. This residue contains sodium carbonate, sodium 
silicate, and other materials, which, to be determined, must be 
dissolved in water and titrated with standard acid, using 
methyl-orange as indicator. 

Free sodium hydroxide. — The alcohol solution of soap is 
titrated with N/10 acid, using phenolphthalein as indicator. 
The titration represents free NaOH present. 

Free oil. — A 5-gram sample is dissolved in water and ex- 
tracted in a separatory funnel with petrol. The petroleum 
ether extract is then washed and evaporated to constant weight 
in a tared dish. 

Oils. — The following methods are taken chiefly from such 
standard texts as Sherman's "Organic Analysis" and Wood- 
man's "Food Analysis." 

A. Lubricating oil. — The color, odor, turbidity, fluores- 



ANALYTICAL METHODS 649 

cence, and general appearance in the standard 4-oz. sample 
bottle are usually noted. 

Soap. — When added to increase the viscosity, soap is 
roughly tested for by seeing whether or not the ash exceeds 
0.05 per cent. 

Rosin oil. — The presence of this oil is determined by the 
Liebermann-Storch reaction, as follows : 5 cc. of acetic an- 
hydride is heated gently with 2 cc. of the oil to be tested. Cool, 
and add a drop or two of 1 : 1 H2SO4 to the anhydride. A 
temporary violet color indicates the presence of rosin or rosin 
oil. 

Saponifiablc oil {qualitative test.) — This is tested for as fol- 
lows : 4 cc. of oil is heated for 15 minutes in a test tube, 
in a paraffin bath with a small piece of sodium. The appear- 
ance of froth or part gelatinization indicates the presence of 
saponifiable oil. 

The saponification number is run if saponifiable oils are 
present. The saponification number in the milligrams of caus- 
tic potash of KOH required to saponify 1 gram of the oil 
can be determined as follows: About 2.5 grams of oil is 
accurately weighed into a 300 cc. Erlenmeyer flask, and 50 
cc. of alcoholic KOH solution (40 grams of KOH in 1 liter 
of • alcohol and filtered) are added; 50 cc. of the alcoholic 
KOH is now placed in a second Erlenmeyer flask to be used 
as a blank. Both flasks are connected to a reflux con- 
denser and boiled for a half-hour. Disconnect, cool, and 
titrate excess KOH with N/2 HC1, using phenolphthalein as 
an indicator. 

Saponification No. 

cc. N/2HC1 for blank— cc. N/2HC1 for sample X 0.028X1000 
weight of sample 

To prevent the alcohol from turning brown by. the action of 
KOH it is allowed to remain in contact with the KOH for 
two weeks, then distilled, and the solution made up as de- 
scribed above. 

Unsaponifiables. — The unsaponifiable material is determined 
by weighing about 3 grams of the oil into a 150 cc. Erlenmeyer 



650 PRACTICAL TANNING 

flask. To this add 25 cc. of alcoholic potash (40 grams per 
liter) and heat with reflux condenser for one hour. Distil 
off the alcohol and add about 75 cc. of water to the residue. 
Stir the solution well and extract in a separatory funnel with 
75 cc. of petroleum ether. Allow the funnel to stand until 
the two solutions have completely separated. Draw off the 
water layer into a second separatory funnel and wash it again 
with petroleum ether, also wash the etheric layer again with 
water ; repeat these washings three or four times. Then com- 
bine all the ether solutions in a weighed flask and combine all 
the water solutions in a beaker. Distil off all ether from the 
weighed flask and heat to constant weight on the water-bath, 
weighing as unsaponifiable matter. The soap solution in the 
beaker can be used for a saponified fatty-acid determination 
by making strongly acid with concentrated hydrochloric acid, 
and dissolving the precipitated fatty acids in ether, 95 per 
cent of the insoluble fatty acids being obtained by this means. 

Percentage of unsaponifiables 

_ weight of unsaponifiable residue X 100 . 

If bad emulsions are encountered in this method, the follow- 
ing dry soap method for unsaponifiables can be run : About 
3 grams of oil is dissolved in alcohol, and saponified as above 
with 2 grams of KOH. The alcohol is distilled off and 3 
grams of NaHCOs and 10 cc. of methyl-alcohol is added. 
The solution is well stirred and evaporated to dryness. 5 
cc. of methyl-alcohol and 10 grams of pure calcium carbonate 
is now added, mixed, and evaporated to dryness at 110° 
C. Extract with petroleum ether, using a Soxhlet extractor. 

Specific gravity. — The specific gravity of the oil is deter- 
mined by use of a hydrometer, specific-gravity bottle, pyk- 
nometer or Westphal balance at 15.5° C. For liquids lighter 
than water the specific gravity can be changed to Be. by use of 
the following formula. 

14° 
°Be = sp. gr. 60 F.— 130. 
60 F. 



ANALYTICAL METHODS 651 

The specific gravity for acids of the same series decreases 
with increasing molecular weight ; in different series the spe- 
cific gravity of corresponding acids increases with the number 
of double bonds and OH groups. 

Cold test. The cold test, or the temperature at which the 
oil just begins to flow, is determined as follows : About 25 
cc. of oil is placed in a tall cylindrical 100 cc. bottle, and a 
thermometer is inserted through the cork so that the bulb 
extends just below the surface of the oil. The bottle is now 
immersed in a mixture of ice and salt. At every fall of 3° 
C. the bottle is removed and inclined until a temperature is 
found where the oil "sets" or just fails to flow. This is the 
cold test. 

Cloud test. — The cloud test or chilling point is the tempera- 
ture at which the oil becomes turbid or cloudy. 

Viscosity. — This is one of the most important determina- 
tions for a lubricating oil. The Engler, Saybolt, and Red- 
wood are the viscosimeters most commonly used. The rela- 
tive viscosity, or body of an oil, is the number of seconds re- 
quired for a certain volume of oil to run through a certain 
orifice at a given temperature, as compared with some standard 
such as distilled water or rape oil. In using the Engler vis- 
cosimeter, 240 cc. of oil is poured into the reservoir. The 
cover is put on, and when the temperature is just 20° C, the 
plug is lifted up, and the number of seconds for 200 cc. to 
flow out is determined. This number, divided by the num- 
ber of seconds necessary for 200 cc. of water to flow out, is 
the Engler viscosity number. Oil employed as a lubricant is 
in a sense used as a cushion, to separate the two moving sur- 
faces and prevent friction. It should have "body" enough to 
stand up, to stay in place and withstand the maximum pres- 
sure that it may be subjected to. On the other hand, if an 
oil is used which has a greater viscosity than is needed, a 
serious loss in power results. Oils of the same kind having 
the same specific gravity and viscosity may safely be substi- 
tuted for each other as lubricants. 



652 PRACTICAL TANNING 

Total acidity. — The acidity of a lubricating oil is impor- 
tant. Organic acids up to 15 per cent (calculated to oleic 
acid) are not especially objectionable, but mineral acids should 
be absent. 

Seven grams of oil is weighed into a 250 cc. glass-stop- 
pered Erlenmeyer flask, and 50 cc. of 85 per cent neutral 
ethyl-alcohol plus 2 drops of phenolphthalein are now added. 
Titrate with N/10 NaOH, shaking well after each addition. 

Mineral acids. — About 12 grams of oil are shaken out re- 
peatedly with hot water until all of the acid is dissolved. Com- 
bine these extracts, filter, cool, and titrate with N/10 NaOH, 
using methyl-orange as indicator. 

Flash-point. — Nearly fill a small evaporating dish or crucible 
with the oil to be tested, and set it deep into a sand-bath. The 
bulb of a thermometer is immersed in the oil, and the sand- 
bath heated with a Bunsen flame. At every 2 degrees rise in 
temperature a small gas flame (such as could be obtained at 
the end of a blowpipe) is moved across the surface of the oil 
at a height of about 1/10 inch. The flash-point is the tem- 
perature at which the first flash is seen. 

Burning point. — This test is carried out as in flash-point 
and is the temperature at which the liquid takes fire. 

Loss on evaporation and tendency to gum. — About 5 grams 
of oil, accurately weighed on a watch-glass, is heated for 
about 5 hours at the maximum temperature to which the oil 
will be subjected in use. The loss in weight should not be 
more than 1 per cent, and the oil should not get gummy. 

Suspended matter. — Any great amount of suspended mat- 
ter could be detected by diluting a sample of oil with petro- 
leum ether, when the suspended matter can easily be seen. The 
open cup or closed cup tests- as applied by the American So- 
ciety for Testing Materials may also be used for this 
determination. 

Anti-fluorescents. — Three cubic centimeters of 10 per cent 
potassium hydroxide solution is added to 1 cc. of oil and 
boiled; a red color shows the presence of anti-fluorescents as 
nitrobenzene. 



ANALYTICAL METHODS " 653 

B. Oil numbers for other than petroleum and lubricat- 
ing oils: Iodine number. — This number is a measure of the 
unsaturation of oil, of the number of double bonds. It is 
determined either by the method of Hubl, Wijs, or Hanus. 
Hubl uses a solution of iodine in alcoholic HgClo. The Wijs 
method uses iodine chloride in place of I -f HgCl 2 , and re- 
quires less time. The Llarius method uses iodine bromide. 
This method has been adopted by the Association of Official 
Agricultural Chemists. It is a rapid method and the solution 
is easily made, as follows : 

(13.2 grams of iodine is dissolved in 1000 cc. of glacial 
acetic acid, and 3 cc. of bromine is added to the cold solution. ) 

Method. — 2.5 grams are weighed into an 8 oz. glass stop- 
pered bottle; 10 cc. of chloroform is now added to dissolve 
the oil and 30 cc. of Hanus solution introduced from a bur- 
ette; 30 cc. of Hanus solution and 10 cc. of chloroform is 
measured into a second bottle and carried along as a blank. 
Let stand for 30 minutes. Add 10 cc. of 15 per cent KI, 
100 cc. of water, and titrate the excess of iodine with N/10 
Na 2 S 2 3 . 

Percentage of iodine 

cc.N /10 iodine for blank — cc. N /10 iodine sample X 0.0127 X 100 
weight of sample 
absorbed. 

Helmer number. — This number is the percentage of insolu- 
ble fatty acids. 

Reichert Meissl number. — The number of cubic centimeters 
of N/10 NaOH to neutralize the soluble volatile acids from 
5 grams of sample. 

Maumene number. — Rise in degrees Centigrade caused by 
the addition of 10 cc. of concentrated H0SO4 to 50 grams of 
oil. This number is dependent on the number of double bonds. 

Acetyl number. — Number of milligrams of KOH to neutral- 
ize the acetic acid obtained by saponification of 1 gram of 
acetylated fat. It is dependent upon the number of OH groups 
in the molecule. 



654 PRACTICAL TANNING 

Titer test. — Temperature of solidification of the mixed fatty 
acids. 

Acid number. — The number of milligrams of KOH to neu- 
tralize the free fatty acid in a one-gram sample. It is de- 
termined by dissolving 5 grams of oil in neutral alcohol, and 
titrating with N/10 KOH, using phenol phthalein as an 
indicator. 

Ester number. — Saponification number — acid number. 

Polenske number. — Cubic centimeters of N/10 NaOH to 
neutralize the insoluble volatile fatty acids, distilled from a 
5 -gram sample. 

Analysis of titanium-potassium oxalate (TiO-z). — Weigh 
accurately 10 grams of sample, dissolve in water, and make 
up to mark in a 250-cc. graduated flask. 

To 25 cc. of the solution add about 5 cc. of concentrated 
sulphuric acid and heat to 60° C. Destroy oxalic acid by add- 
ing potassium permanganate solution slowly to the hot solu- 
tion until a permanent pink color results. Just enough solid 
sodium bisulphite is now added to destroy the excess potas- 
sium permanganate and dissolve any manganese dioxide which 
may be formed; ammonium hydroxide is added in slight ex- 
cess. Acetic acid is added in considerable excess (about 15 
cc. 1:3 acid), and the solution digested on the hot plate for 
about 20 minutes. Filter off the precipitated TiC>2 while the 
solution is hot. Wash the precipitate with hot water until free 
from sulphates ; ignite in a weighed crucible, and weigh as 
TiC>2. This determination is accurate in the absence of iron 
and aluminum, the acetic acid preventing the manganese from 
being precipitated. 

If iron and aluminum are present, the following modifica- 
tions should be made. Carry out the precipitation with am- 
monium hydroxide and acetic acid as described above, filter 
and wash. Dissolve the precipitate in about 15 cc. of HC1 
(sp. gr. 1.12). Stir a minute in the cold, then boil two or 
three minutes. Any undissolved material can be dissolved by 
adding a few drops of concentrated HNO3 and boiling. Di- 
lute, filter, and evaporate to destroy excess of acid. Dilute 



ANALYTICAL METHODS 655 

to about 20 cc, and make alkaline with an excess of NaOH 
(avoid too great an excess) . Add 5 cc. of 10 per cent Na2C03, 
boil, cool, add an equal volume of water and -filter. 
Aluminum remains in the filtrate in the form of NaAlC>2, and 
iron and titanium become insoluble and are collected on the 
filter-paper as hydroxides or oxides. 

Aluminum. — This is determined in the usual way. Make 
the solution acid with HC1, then faintly alkaline with NH4OH, 
boil, filter, ignite, and weigh up AI2O3. 

Iron and titanium. — Dissolve the iron and titanium residue 
obtained above in the least possible amount of HC1 (1.12 sp. 
gr.). Add 20 cc. more HC1 (1.12 sp. gr.), and transfer the 
cold solution to a separatory funnel. Add an equal volume 
of ether and shake vigorously. Allow the two layers to sep- 
arate and draw them off into two separate beakers. Rinse 
out the funnel with a little ether. Return the aqueous layer 
to the funnel and treat with ether as before. Repeat this 
treatment until the ether layer is colorless. Iron is now in 
the ether layer in the form of FeClj. Combine these extrac- 
tions, distil off the ether and determine iron in the usual way. 
The titanium is found in the water extract from which it can 
be precipitated as TiC>2 or TiO (OH) 2 as directed above. 

Oxalate. — Acidify 10 cc. of the original solution with 
H2SO4, heat to 60° C, and titrate with N/10 KMn0 4 as in 
an ordinary permanganate titration. 

1 cc N/10 KMn0 4 = 0.0044 gram C2O4 

Ash. — One gram of sample is ignited at a low red heat in 
a platinum dish. After igniting, the dish is transferred to a 
desiccator and weighed as soon as cool. Repeat the heating 
to constant weight ; providing other metals are absent the ash 
is composed of TiC>2 and K2CO3. 

Potassium. — The percentages of potassium and water are 
usually obtained by subtracting the sum of the above per- 
centages from 100. 

The potassium may be determined as follows: A 1-gram 
sample is dissolved in 50 cc. of hot water. Filter, wash the 



656 PRACTICAL TANNING 

filter-paper with hot water, and reject any insoluble residue. 
If sulphates are present, they must be removed by precipi- 
tating with BaCl2 in the usual way. The excess of barium, 
and any aluminum which may be present, must now be re- 
moved by making the solution alkaline with NH4OH, heating, 
and adding ammonium carbonate solution until no further 
precipitation occurs. Filter, wash, and proceed with the fil- 
trate as follows : Evaporate the solution to 20 cc. and add 
10 to 15 cc. of perchloric acid. Evaporate, with stirring, in 
a porcelain dish, until the solution becomes syrupy. Dilute 
and evaporate again until dense white fumes of perchloric acid 
are seen. Cool, and introduce 25 cc. of 95 per cent alcohol, 
to which 1 cc. of perchloric acid has been added. Stir well 
and allow to settle. Decant the clear portion through a 
weighed Gooch crucible and treat twice with 25 cc. of the al- 
coholic wash. Throw the insoluble portion on the Gooch, 
wash with 25 cc. of alcohol containing two drops of perchloric 
acid. Then wash with 95 per cent alcohol. Cover the Gooch 
crucible, and dry in an oven at a temperature of about 130° 
C. Weigh as KCIO4. Report potassium as KoO. 

Analysis of blood albumen. — The sample should be finely 
powdered and put into a well-covered vessel. 

Water. — Dry 2 grams of the sample in a tared dish to con- 
stant weight at 100° C. Loss in weight is the water. 

Ash. — Ignite 2 grams of the sample at a very low temper- 
ature in a platinum dish until all the carbon is burned off. 
Weigh as ash. 

Insoluble matter. — Dissolve 5 grams of the sample in water 
and dilute to 250 cc. Pour some of this solution into a glass, 
add 2 or 3 grams of kaolin, stir well and pour into a fluted 
filter. Collect 50 cc. of the filtrate as soon as it runs clear, 
and evaporate to dryness in a tared dish. Evaporate 50 
cc. of the unfiltered and well-shaken solution in another dish. 
The difference in weight of the two residues represents the 
insoluble matter. 

Non-albumen. — Dilute 50 cc. of the solution used in the 
above determination in water, and make slightly acid to litmus 



ANALYTICAL METHODS - 657 

with acetic acid. Digest on steam-bath until the albumen is 
all precipitated and the supernatant liquid appears clear. Wash 
into a 250 cc. flask, cool, make up to the mark, filter, and 
evaporate 50 cc. in a tared dish. The residue represents non- 
albumen. 

Analysis of formic acid. — The specific gravity is taken at 
60° F. with a Westphal balance. 

Total acidity. — Between 50 and 60 grams of the sample is 
dissolved in water, and diluted to 1000 cc. ; 25 cc. of this 
solution is titrated with N/10 NaOH, using phenolphthalein 
as indicator. The result is calculated to formic acid. 

Acetic acid. — Add about 5 grams of yellow mercuric oxide 
to about 10 cc. of the solution used in the above determination. 
Dilute to about 150 cc. and digest on the steam-bath for about 
1£ hours. Filter through a fluted filter, using kaolin if nec- 
essary to obtain a clear filtrate. If acetic acid is present, a 
black precipitate will form in the filtrate on the addition of 
ammonium sulphide. 

Mineral acids. — The S0 4 and CI ions are tested for in the 
regular manner. 

Analysis of egg-yolk: Water. — A glass evaporating dish 
containing some purified quartz and a small glass rod is dried 
in the oven to constant weight. A sample of 5 or 6 grams 
is weighed from the weighing bottle and thoroughly mixed 
with the sand in the dish. The dish is heated in the oven at 
100° C, with occasional stirring to break up any lumps 
formed, and dried to constant weight. The loss is calculated 
as water. 

'Ash. — A sample of 2 or 3 grams is ignited at a low tem- 
perature in a platinum dish until charred. The carbonaceous 
mass is extracted with hot water and filtered into a tared dish, 
then evaporated to dryness. The filtrate is ignited and the 
residue added to the extracted portion. The sum represents 
the ash. 

Fat. — The portion used for the determination of water is 
removed from the dish, powdered finely in the mortar and 
extracted with petroleum ether in a Soxhlet extractor. The 



658 PRACTICAL TANNING 

extract is evaporated to dryness at 100° C, and weighed as 
fat. 

Salt. — After removing the fat, the sample is extracted with 
hot water, cooled, and made up to 250 cc, and 50 cc. of this 
solution is then titrated with N/10 AgNOa, using potassium 
chromate as an indicator. 

Nitrogen or albumen. — Three or four grams of the original 
sample is digested with 15 cc. of concentrated H2SO4 and 10 
grams of potassium sulphate until clear. The digested portion 
is diluted with water, connected to a condenser, an excess of 
sodium hydroxide is added, the ammonia distilled into 50 cc. 
N/10 acid, and the determination completed as previously 
described under the Kjeldahl method. The nitrogen multiplied 
by 6.33 equals albumen. 

Analysis of acetate of iron liquor. — 25 grams of the 
sample is weighed out and diluted to 250 cc. 

Total acidity. — 25 cc. of N/10 NaOH is added to 50 cc. 
of the above solution in a 250 cc. flask, the solution made 
up to the mark, shaken, and filtered; 50 cc. of the filtrate 
is titrated with N/10 H2SO4, using phenolphthalein as 
indicator. The result may be calculated to acetic acid. 

Iron oxide. — 50 cc. of the above solution is digested to 
clearness with concentrated H0SO4 in a Kjeldahl flask to 
destroy organic matter. The digested portion is made up 
to 250 cc, and 100 cc. is precipitated with ammonium 
hydroxide in the regular manner for the determination for 
Fe203. 

Ash. — Ignite 1 gram of the sample in a platinum dish. 

Sulphuric acid. — Test for SO4, and if present, proceed as 
follows : 10 grams of the sample is made up to 250 cc. ; 
25 cc. of the solution is measured into a platinum dish with 
25 cc. of N/10 Na2CO,3, evaporated to dryness, and ignited. 
The residue is re-dissolved in water and titrated back with 
N/10 H2SO4. The titration thus obtained subtracted from 
25 represents in cubic centimeters of N/10 alkali the acid 
present as free and combined H2SO4. The acid may also be 
determined gravimetrically by precipitation with BaC^. Any 



ANALYTICAL METHODS - 659 

FeSCU present may be calculated from these two determina- 
tions and the determination of acetic acid by distillation. 

Acetic acid. — In the presence of mineral acids, the acetic 
acid should be distilled off. This is done by dissolving a 
few grams of the sample in water, acidifying with H2SO4, 
and distilling until no more acid is obtained in the distillate. 
This will require thorough distillation. 

Some simple chemical tests for leather makers.* — The 
following are a few simple tests which may be applied to 
several of the more common materials used in the tannery 
without the aid of a specially arranged laboratory or any 
expensive apparatus, in order to tell whether or not they are 
adulterated. 

Lime. — A good quicklime should slake well when mixed 
with water. If, on the addition of a little hydrochloric acid, 
it effervesces, it points to a fair amount of chalk present ; while 
if after this treatment with acid much is left undissolved, it 
would indicate an excessive quantity of sand or insoluble 
matter. 

Linseed meal (crushed linseed). — Make a solution in hot 
water, and allow to cool. When cold, add a few drops of 
tincture of iodine. A blue color formed would show that the 
linseed had been adulterated (the blue color really indicates 
the presence of starch, and pure linseed contains no starch). 

Dried blood. — If the amount of ash is determined, it 
should be between 4 and 5 per cent. The ash should be white, 
and if it is a brick-red color the admixture of iron would be 
indicated. 

Gum arabic. — The likely adulterant is gum tragacanth. 
Dissolve some of the gum, after finely powdering, in the 
blue solution obtained by adding ammonia to a solution of 
copper sulphate. If an appreciable amount is left undissolved, 
tragacanth is probably present. 

Dyes. — To determine whether a dye is just a simple one or 
an admixture, the following procedure should be adopted : 
Place a small portion of the dye on the end of a penknife, 



Jour. Amer. Leather Chemists, Dec, 1916. 



660 PRACTICAL TANNING 

and blow it onto a piece of wet white blotting paper held 
about a foot away. The small particles will adhere to 
the wet paper and dissolve in the water, showing its color. 
By this method one may show, for example, that a dye consists 
of a mixture of a blue and a red dye. 

Cod-liver oil. — This is likely to be adulterated with mineral 
oil. Boil two or three drops of the oil with caustic soda 
which has been dissolved in methylated spirit. If after con- 
tinued boiling a perceptible amount is left undissolved this 
would indicate admixture with mineral oil. This test is based 
upon the fact that, under the influence of caustic soda, cod 
oil is converted into soap, whereas mineral oils are not so 
changed. 

Glucose. — This substance may be adulterated, and if a small 
piece is burnt in a tin, only a very small amount of a white 
ash is left. Anything over a trace would indicate adulterants. 

Salt. — Impure salt may contain a small yet undesirable 
amount of iron. To test for this, make a solution of the salt 
in water, and add a few drops of potassium thiocyanate. A 
red color will develop in the presence of the iron. If this 
chemical is not at hand, add a few drops of potassium ferro- 
cyanide (yellow prussiate of potash), when a blue color will 
indicate iron. 

Ammonium chloride (sal-ammoniac). — This should be of a 
pure white color, and perfectly soluble in cold water. If a 
small amount is heated in a tin lid over a gas flame it will be 
completely volatilized, no residue being left. 

Caustic soda, — This substance, if left exposed to the air, 
will absorb carbon dioxide therefrom, and so gradually 
"carbonate." A rough test would be to dissolve a small sample 
in cold water, and then add a little hydrochloric or sulphuric 
acid (dilute). If gas bubbles are given off, this would indicate 
carbonates, which should not be present in a good sampl 

Ferrous sulphate (green vitriol). — A good sample should 
be of a uniform pale green color. In a moist atmosphere it is 
liable to undergo oxidation, in which case a brownish color 



ANALYTICAL METHODS - 061 

will develop. To prevent this, the material should be kept in 
a cool, dry place, for preference in large stone jars fitted 
with bungs. 

Sodium thiosulphate {hypo). — It is quite unlikely that this 
chemical will be adulterated, but as in appearance it resembles 
soda it may be confused with it if, say, the labels became 
detached from the receptacles in which they were kept. Add 
a little hydrochloric acid to a solution of the substance in 
water. If hypo, the solution will turn yellow (owing to the 
fine precipitate of sulphur), and an unpleasant-smelling gas 
will be evolved (sulphur dioxide). If, on the other hand, the 
substance be soda, only bubbles of an odorless gas will be 
given off (carbon dioxide). 

Flour. — Alum is sometimes added to a bad quality of flour 
to improve its appearance. To test for this substance, the 
following reagent has to be prepared : 10 cc. of 5 per cent 
alcoholic logwood solution mixed with 150 cc. of water, and 
10 cc. of saturated ammonium carbonate solution (this reagent 
should be mixed just before using). Some of the flour to be 
tested is made into a paste with water, and then a few drops 
of the solution added. Alum, if present, will be indicated by 
the formation of a blue color after the mixture has been 
allowed to stand for about two hours. 

The percentage of ash also affords a good method of deter- 
mining the quality of a flour. High-class flour yields 0.5 per 
cent of ash, whereas lower qualities will give from 0.5 up to 
8 per cent, according to how much bran is present. Chalk, 
which some years ago was used as an adulterant, can be tested 
for by adding dilute hydrochloric acid to some flour paste, 
when an effervescence will take place if chalk is present. 

Egg-yolk. — It is difficult to suggest any simple tests for the 
purity of egg-yolk, a chemical analysis being essential. The 
following tests, however, will detect the preservative present : 
Ignite some of the yolk to complete ash in a porcelain basin. 
If a large amount of a white ash is left, salt (sodium chloride) 
is the preserving agent. Now add a few drops of sulphuric 



662 PRACTICAL TANNING 

acid to the ash and then some methylated spirit; warm the 
whole, and then ignite the spirit. In the presence of boric acid, 
a greenish tinge will appear around the edges of the flame. 

Ammonia or ammonium hydroxide. — This is a solution of 
pure ammonia gas in water, and at its greatest strength has a 
specific gravity of 0.880. A higher gravity than this would 
indicate either a weak liquor or the addition of water. If 
some of the solution is boiled to dryness in a dish, no residue 
should be left. Sulphates, chlorides, and other impurities are 
deposited by this treatment. 

Borax. — It is unlikely that this substance will appear adulter- 
ated, although it is stated that soda has been used for this 
purpose. This could be detected by treating some of the borax 
with dilute hydrochloric acid, when, if soda is present, 
bubbles of gas will be evolved. 

Mineral acids. — The two acids of this class used are hydro- 
chloric and sulphuric, and to distinguish between them the 
following tests may be applied: Add to the acid (previously 
diluted with a little distilled water) a small quantity of silver 
nitrate solution. If a precipitate is formed, hydrochloric acid 
will be indicated. Using a fresh sample of the diluted acid, 
repeat the above experiment, using a solution of barium 
chloride in place of silver nitrate. A white precipitate will 
show sulphuric acid. By these tests, small amounts of impu- 
rities may be detected in either acid ; for example, a very slight 
precipitate in the case of the first test will show a trace of 
chloride, etc. Iron may be detected in either acid bv means 
of potassium sulphocyanide. 

Shellac. — The only impurity which can be identified in 
a simple manner is any weighting material added, such as sand, 
etc., which may also be present in a dirty sample. Such sub- 
stances will be left behind as insoluble residue when some of 
the material is dissolved in hot methylated spirit or hot 
ammonia solution. A good sample will dissolve completely in 
either of these two solvents. Shellac is often adulterated with 
rosin, but its detection is too complicated to include in these 
tests. 



ANALYTICAL METHODS 663 

Soda. — Washing soda or sodium carbonate may contain 
iron and salt. Take some of the sample, and dissolve it in 
dilute sulphuric acid ; or better still, in some dilute nitric acid. 
Divide the solution into two parts, and to one add a few drops 
of silver nitrate solution, when a white curdy precipitate will 
show the presence of salt (if only a white cloudiness appears, 
a trace of salt is present). To the other half of the solution 
add some potassium sulphocyanide, when a blood-red colora- 
tion will indicate iron. 

Carbolic acid or phenol. — This, sometimes used as an anti- 
septic, is liable to contain an undesirable amount of iron. The 
following method will apply : About half an ounce of the 
sample should be burned to ash in a porcelain dish. The opera- 
tion must be performed in a place where the fumes evolved 
can be carried away. Then dissolve the ash in a few drops of 
strong nitric acid and dilute with a little water. The usual test 
for iron with potassium sulphocyanide may then be applied. 

Sumac. — The purity of this material, like all other tanning- 
materials, can only be determined by an accurate chemical 
examination. Iron in a metallic form may sometimes be pres- 
ent in an undesirable amount. This may be tested for by run- 
ning a strong magnet through a sample of the sumac previously 
spread out in a thin layer. The particles of iron will adhere 
to the magnet and may be removed and further examined if 
necessary. 

Lactic acid. — If this acid has been adulterated with mineral 
matter, a large amount of residue will be left when some of the 
acid is boiled to dryness in a porcelain dish. To test for iron, 
the residue obtained above is dissolved in a little nitric 
acid diluted with a small quantity of water, and a solution 
of potassium sulphocyanide added. If present, iron will give 
a deep red color. 

(Note: — This test also applies to acetic or formic acid.) 

Soaps. — These, whether hard or soft, are very liable to 
adulteration with various admixtures. The sample should be 
cut into very small pieces, and a little of it boiled in absolute 
alcohol (or very good re-distilled methylated spirit may be 



664, PRACTICAL TANNING 

used). Only soap will be dissolved by this treatment. What 
is left will be alkaline carbonate, borate, silicate, together with 
any "filling" material, such as starch, chalk, and, in very bad 
cases, even sawdust. 

( Note : — It might be added that to detect iron in any material 
containing a large amount of organic matter, the following 
method may always be applied: Burn the material to an ash 
in a porcelain (or better still a platinum) dish, and then heat the 
ash and, when cool, treat with nitric acid. The addition of this 
acid is important, inasmuch as it converts all the iron present 
into the ferric condition, which is essential for the final test. 
Having now got the iron into solution in this form, the liquid 
is diluted with a little water, and then a little 10 per cent 
potassium sulphocyanide solution is added, when a red color 
shows the presence of iron. If preferred, a 10 per cent solu- 
tion of potassium ferrocyanide may be used instead of the 
sulphocyanide. In this case, however, a deep blue color will 
be produced if iron be present.. 

Indicators. — By means of indicators we are able to tell 
whether a liquor has an acid or alkaline reaction. The fol- 
lowing table gives the colors produced when using these vari- 
ous indicators : 

Indicator If acid If alkaline 

Litmus Red Blue 

Methyl-orange Red Yellow 

Phenolphthalein Colorless Red 



CHAPTER XXII 
DISPOSAL OF TANNERY WASTE* 

Tanneries are among the largest producers of industrial 
organic wastes. Each day's run-off consists of many millions 
of gallons of liquid material teeming with bacteria and con- 
taining much organic matter, both dissolved and suspended, 
and of a highly putrescible nature. Up to the present time 
practically all tanneries have been discharging this waste into 
streams, lakes, or sewer systems without preliminary treat- 
ment. The situation, however, is rapidly becoming acute, 
inasmuch as municipalities and boards of health are begin- 
ning to prohibit by law the pollution, directly or indirectly, of 
natural waters by industrial wastes. Where tanneries dis- 
charge their waste into local sewer systems authorities are at 
least insisting that suspended matter be excluded so that the 
sewers shall not become clogged. Where cities are treating as 
well as collecting their sewage and industrial waste, they are 
stipulating that all materials harmful or burdensome to the 
disposal plant processes shall be excluded, or reduced by di- 
lution to such a degree that the waste can be successfully and 
economically treated. In fact, the policy now followed in some 
localities is to insist that no industrial effluent stronger than 
the average sanitary sewage be permitted to enter the local 
sewer system. Thus it is readily seen that the problem of dis- 
posing of tannery waste, especially where the tanner is com- 
pelled to treat his own material, is fast becoming important 
and serious. 

Classification and Nature of Tannery Wastes. 

1. Soak liquors — containing blood, manure, hair, etc. 

2. Lime liquors — containing lime and magnesia, calcium 
carbonate, hair, and dissolved hide substance. 

*The material contained in this chapter was furnished by Victor H 
Kadish of Milwaukee, Wisconsin. 

665 



666 PRACTICAL TANNING 

3. Bate liquors — containing bacteria, enzymes, hide sub- 
stance, etc. 

4. Pickle liquors — containing salt and acid in solution; and 
calcium sulphate in suspension. 

5. Chrome tanning liquors — containing salts in solution; 
chromium compounds in solution or suspension. 

6. Vegetable tanning liquors — containing tannins, "reds," 
coloring matter, etc. 

7. Dye liquors — consisting of solutions of weak dyestuffs. 

8. Fat-liquors — containing small quantities of oils and fats. 

9. Wash waters — in large volumes containing undissolved 
or suspended solids which, when removed, leave practically 
pure water. 

10. Condenser water. 

Plain sedimentation. — This is the simplest and most com- 
mon method now used. The sewage flows continuously 
at a low velocity through a settling-tank or basin, properly 
baffled, with the consequent settling out of a considerable 
percentage of the material in suspension. The supernatant 
liquor is drawn off at intervals, and the accumulated sludge 
is removed from the bottom of the tank. While the plant 
cost is low and operating charges are small, there are many 
disadvantages in this method, a few being the large floor area 
required, a serious objection in many cases; instability of the 
effluent with very little if any reduction in the number of 
bacteria ; difficulty in removal and disposal of the sludge which 
is very offensive in odor and has little value as a fertilizer. 

Mechanical sedimentation. — This is usually carried out in 
a circular tank with sloping bottom by means of slowly ro- 
tating arms which tend to scrub the solids towards the bottom 
of the sedimentation tank where they can be withdrawn by 
means of a pump or syphon. The sludge as withdrawn is in 
the liquid condition, containing about 95 per cent water, which 
necessitates de-watering before it can be disposed of. This 
method increases the rate of settling of the solids and pro- 
vides a cleaner-cut handling of the sludge, but the same ob- 



DISPOSAL OF TANNERY WASTE ' 667 

jections, nevertheless, maintain as above, only to a lesser 
degree. 

With either method further treatment of the effluent is 
necessary if it is to be rendered relatively stable and low 
in bacteria. This can be. accomplished by means of coarse 
stone trickling niters, which again occupy much space, or the 
effluent may be disinfected by means of liquid chlorine which 
largely reduces the number of bacteria when sufficient chlor- 
ine is used. 

Activated sludge process. — This is a recently developed 
rapid aeration process which produces a remarkably pure 
effluent when applied to sanitary sewage. The raw sewage 
flows through rectangular tanks fitted with "filtros" plates in 
the bottom through which finely divided compressed air is 
diffused, thereby agitating the sewage violently. About 20 
per cent by volume of the thickened so-called activated sludge 
is mixed with the incoming raw sewage as it enters the aera- 
tion tank. This combination of air and activated sludge pre- 
cipitates a large portion of the organic matter in the form of 
a light, fluffy, brown-colored mass which is separated from 
the clear, purified liquor in a settling tank by means of a Dorr 
thickener. That portion of the sludge withdrawn from the 
settling tank and not returned to the aerating system must be 
de-watered by pressing or otherwise. This is no small prob- 
lem when the nature of the material and its 98 per cent mois- 
ture content is considered. The process as a whole is delicate 
of control and costly, and while in its present stage of devel- 
opment looks promising for large municipal sewage disposal 
works, is hardly feasible on the small scale of tannery 
operation. 

Other methods of treatment. — Heretofore, in the relatively 
few installations for tannery waste disposal, it has been the 
practice to collect the entire flow of the tannery and treat it 
at the disposal plant, disregarding the fact that fully 80 per 
cent of the volume is practically clean water. Handling 
large volumes means increased costs, necessity for large 
ground areas— frequently not available — and generally is a 



668 PRACTICAL TANNING 

heavy financial burden to the tanner, without adequate return. 
Advantage should be taken of this large volume of almost 
clean water by laying out a dual sewer system, one for the 
collection of foul and polluted waste, the other for the much 
larger volume of wash and condenser water. The latter can 
be merely passed through a suitable screen to remove the 
coarse solids in suspension such as hair, bits of flesh, tanned 
shavings, etc., after which the clear effluent can be conducted 
away from the tannery. The second and smaller system 
should of course collect all of the polluted waste for subse- 
quent treatment. With a greatly reduced volume to be treated, 
and richer in solids as well, treatment in a mechanical sedi- 
mentation tank is feasible and economical. If, however, the 
required ground area is not available, the use of a recently 
perfected, continuously operating centrifugal machine, the so- 
called "ter meer," made in Germany, is suggested. This 
machine, occupying only a few square feet of floor space, will 
"scrub out" 95 per cent of the suspended matter in the form 
of 80 per cent moisture sludge-cake, discharged automati- 
cally, and deliver at the same time a clear effluent. No 
further treatment should be necessary where the tannery waste 
is being run into a municipal sewer system. Where it is being 
discharged into a potential water supply, final treatment of 
the effluent from settling tank or centrifuge with liquid chlor- 
ine is suggested. 

Another recent discovery may change the recovery of tan- 
nery waste from the debit to the credit side : By using the 
so-called sulphide process for de-hairing, whereby the hair is 
completely dissolved, it is now commercially profitable to 
recover this waste sulphide liquor as fertilizer and at the same 
time remove from tannery waste a large percentage of the 
most obnoxious material. When spent sulphide liquors are 
rendered slightly acid, the dissolved hair (proteid colloids) is 
immediately precipitated in the form of a spongy, porous mass 
from which the water is readily expressed. This can be 
accomplished by means of a continuously operating process 
which runs itself automatically, consisting of very simple 



DISPOSAL OF TANNERY WASTE 669 

equipment and requiring little labor. The resulting fertilizer 
material is uniform in composition and averages 13 per cent 
ammonia on a 10 per cent moisture basis, with 97 per cent 
of the ammonia available. This material ranks with the best 
grade of packer tankage, and should always command a ready 
market. At present fertilizer prices the manufacturing profit 
amounts approximately to 100 per cent. An interesting side- 
light in this connection is that the process provides for the 
recovery of a considerable portion of the original sodium sul- 
phide used, which, together with the fertilizer produced, makes 
the sulphide de-hairing process much cheaper per unit of 
leather than the liming process. 

By segregating tannery waste liquors into two classes as 
indicated, and by adopting the sulphide process with recov- 
ery of the spent sulphide waste as a valuable nitrogenous 
fertilizer material, the tanner can clean up his back yard and 
make a profit at the same time. 



CHAPTER XXIII 

USEFUL DATA 

Thermometer conversions. — To convert degrees Centi- 
grade into Fahrenheit (above freezing) multiply by 9, divide 
the product by 5 and add 32 to the quotient. 

To convert Fahrenheit (above freezing) into Centigrade, 
subtract 32, multiply the remainder by 5 and divide the prod- 
uct by 9. 

To convert Reaumur into Fahrenheit, multiply by 9, divide 
the product by 4 and add 32 to the quotient. 

To convert Fahrenheit into Reaumur, subtract 32, multiply 
the remainder by 4 and divide the product by 9. 





Boiling and Freezing Points of Thermometers 






Boiling 
Point 


Freezing 
Point 


Fahrenheit 




212° 

100° 

80° 


32° 


Centigrade 




0° 




0° 







FORMULA FOR CALCULATING THE WEIGHT OF PIPES 

W = k(D'— d") 

W = weight of 1 lineal foot in lbs. 
D = outside diameter in inches, 
d =• inside diameter in inches, 
k ■— a coefficient, being 

0.85 for aluminum. 

2.43 for zinc. 

2.45 for cast iron. 

2.49 for tin. 

2.64 for wrought iron. 

2.82 for brass. 

3.03 for copper. 

3.86 for lead. 

670 







USEFUL 


, DATA 




671 




Comparisons of Thermometers 




Fahrenheit 


Centigrade 


Reaumur 


Fahrenheit 


Centigrade 


Reaumur 


212 


100. 


80. 


142 


61.1 


48.9 


210 


98.9 


79.1 


140 


60. 


• 48. 


208 


97.8 


78.2 


138 


58.9 


47.1 


206 


96.7 


77.3 


136 


57.8 


46.2 


204 


95.6 


76.4 


134 


56.7 


45.3 


202 


94.4 


75.6 


132 


55.6 


44.4 


200 


93.3 


74.7 


130 


54.4 


43.6 


198 


92.2 


_ 73.8 


128 


53.3 


42.7 


196 


91.1 


72.9 


126 


52.2 


41.8 


194 


90. 


72. 


124 


51.1 


40.9 


192 


88.9 


71.1 


122 


50. 


40. 


190 


87.8 


70.2 


120 


48.9 


39.1 


188 


86.7 


69.3 


118 


47.8 


38.2 


186 


85.6 


68.4 


116 


46.7 


37.3 


184 


84.4 


67.6 


114 


45.6 


36.4 


182 


83.3 


66.7 


112 


44.4 


35.6 


180 


82.2 


65.8 


110 


43.3 


34.7 


178 


81.1 


64.9 


108 


42.2 


33.8 


176 


80. 


64. 


106 


41.1 


32.9 


174 


78.9 


63.1 


104 


48. 


32. 


172 


77.8 


62.2 


102 


38.9 


31.1 


170 


76.7 


61.3 


100 


37.8 


30.2 


168 


75.6 


60.4 


98 


36.7 


29.3 


166 


74.4 


59.6 


96 


35.5 


28.4 


164 


73.3 


58.7 


94 


34.4 


27.6 


162 


72.2 


57.8 


92 


33.3 


26.7 


160 


71.1 


56.9 


90 


32.2 


25.8 


158 


70. 


56. 


88 


31.1 


24.9 


156 


68.9 


55.1 


86 


30. 


24. 


154 


67.8 


54.2 


84 


28.9 


23.1 


152 


66.7 


53.3 


82 


27.8 


22.2 


150 


65.6 


52.4 


80 


26.7 


21.3 


148 


64.4 


51.6 


78 


25.6 


20.4 


146 


63.3 


50.7 


76 


24.4 


19.6 


144 


62.2 


49.8 


74 


23.3 


18.7 



672 



PRACTICAL TANNING 



Comparison of thermometers (concluded) 



Fahrenheit 


Centigrade 


R6aumur 


Fahrenheit 


Centigrade 


Reaumur 


72 


22.2 


17.8 


6 


—14.4 


—11.6 


70 


21.1 


16.9 


4 


—15.6 


—12.4 


68 


20. 


15. 


2 


—16.7 


—13.3 


66 


18.9 


15.1 





—17.8 


—14.2 


64 


17.8 


14.2 


—2 


—18.9 


—15.1 


62 


16.7 


13.3 


—4 


—20. 


—16. 


60 


15.6 


12.4 


—6 


—21.1 


—16.9 


58 


14.4 


11.6 


—8 


—22.2 


—17.8 


56 


13.3 


10.7 


—10 


—23.3 


—18.7 


54 


12.2 


9.8 


—12 


—24.4 


—19.6 


52 


11.1 


8.9 


—14 


—25.6 


—20.4 


50 


10. 


8. 


—16 


—26.7 


—21.3 


.48 


8.9 


7.1 


—18 


—27.8 


—22.2 


46 


7.8 


6.2 


—20 


—28.9 


—23.1 


44 


6.7 


5.3 


—22 


—30. 


—24. 


42 


5.6 


4.4 


—24 


—31.1 


—24.9 


40 


4.4 


3.6 


—26 


—32.2 


—25.8 


38 


3.3 


2.7 


—28 


—33.3 


—26.7 


36 


2.2 


1.8 


—30 


—34.4 


—27.6 


34 


1.1 


0.9 


—32 


—35.6 


—28.4 


• 32 


0. 


0. 


—34 


—36.7 


—29.3 


30 


—1.1 


—0.9 


—36 


—37.8 


—30.2 


28 


—2.1 


—1.8 


—38 


—38.9 


—31.1 


26 


—3.3 


—2.7 


—40 


—40. 


—32. 


24 


—4.4 


—3.6 


—42 


—41.1 


—32.9 


22 


—5.6 


—4.4 


—44 


—41.2 


—33.3 


20 


—6.7 


—5.3 


—46 


—43.3 


—34.7 


18 


—7.8 


—6.2 


—48 


—44.4 


—35.6 


16 


—8.9 


—7.1 


—50 


—45.6 


—36.4 


14 


—10. 


—8. 


—52 


—46.7 


—37.3 


12 


—11.1 


—8.9 


—54 


—47.8 


—38.2 


10 


—12.2 


—9.8 


—56 


—48.9 


—39.1 


8 


—13.3 


—10.7 









USEFUL DATA G73 

Specific gravity, degrees Twaddell, barkometer, and Baume 



Specific 


Twaddell 


Barko- 


Baume' 


Specific 


Twaddell 


Barko- 


Baum£ 


Gravity 




meter 




Gravity 




meter 




1.000 











1.205 


41 


205 


24.5 


1.005 


1 


5 


0.7 


1.210 


42 


210 


25.0 


1.010 


2 


10 


1.4 


1.215 


43 


215 


25.5 


1.015 


3 


15 


2.1 


1.220 


44 


220 


26.0 


1.020 


4 


20 


2.7 


1.225 


45 


225 


26.4 


1.025 


5 


25 


3.4 


1.230 


46 


230 


26.9 


1.030 


6 


30 


4.1 


1.235 


47 


235 


27.4 


1.035 


7 


35 


4.7 


1.240 


48 


240 


27.9 


1.040 


8 


40 


5.4 


1.245 


49 


245 


28.4 


1.045 


9 


45 


6.0 


1.250 


50 


250 


28.8 


1.050 


10 


50 


6.7 


1.255 


51 


255 


29.3 


1.055 


11 


55 


7.4 


1.260 


52 


260 


29.7 


1.060 


12 


60 


8.0 


1.265 


53 


265 


30.2 


1.065 


13 


65 


8.7 


1.270 


54 


270 


30.6 


1.070 


14 


70 


9.4 


1.275 


55 


275 


31.1 


1.075 


15 


75 


10.0 


1.280 


56 


280 


31.5 


1.080 


16 


80 


10.6 


1.285 


57 


285 


32.0 


1.085 


17 


85 


11.2 


1.290 


58 


290 


32.4 


1.090 


18 


90 


11.9 


1.295 


59 


295 


32.8 


1.095 


19 


95 


12.4 


1.300 


60 


300 


33.3 


1.100 


20 


100 


13.0 


1.305 


61 


305 


33.7 


1.105 


21 


105 


13.6 


1.310 


62 


310 


34.2 


1.110 


22 


110 


14.2 


1.315 


63 


315 


34.6 


1.115 


23 


115 


14.9 


1.320 


64 


320 


35.0 


1.120 


24 


120 


15.4 


1.325 


65 


325 


35.4 


1.125 


25 


125 


16.0 


1.330 


66 


330 


35.8 


1.130 


26 


130 


16.5 


1.335 


67 


335 


36.2 


1.135 


27 


135 


17.1 


1.340 


68 


340 


36.6 


1.140 


28 


140 


17.7 


1.345 


69 


345 


37.0 


1.145 


29 


145 


18.3 


1.350 


70 


350 


37.4 


1.150 


30 


150 


18.8 


1.355 


71 


355 


37.8 


1.155 


31 


155 


19.3 


1.360 


72 


360 


38.2 


1.160 


32 


160 


19.8 


1.365 


73 


365 


38.6 


1.165 


33 


165 


20.3 


1.370 


74 


370 


39.0 


1.170 


34 


170 


20.9 


1.375 


75 


375 


39.4 


1.175 


35 


175 


21.4 


1.380 


76 


380 


39.8 


1.180 


36 


180 


22.0 


1.385 


77 


385 


40. 1 


1.185 


37 


185 


22.5 


1.390 


78 


390 


40.5 


1.190 


38 


190 


23.0 


1.395 


79 


395 


40.8 


1.195 


39 


195 


23.5 


1.400 


80 


400 


41.2 


1.200 


40 


200 


24.0 











674 PRACTICAL TANNING 

Weight and specific gravity of liquids 

Water. — The weight of fresh water is, in practise, usually 
assumed at 62^ pounds per cubic foot, but 62^ would be 
more nearly correct at ordinary temperatures, about 60° F. A 
pound of , water is equal to 27.759 cubic inches. 



Specific 
Gravity 



Weight in 
Pounds per 
Cubic Inch 



Weight in 

Pounds per 

Gallon 



Water, distilled, 60° F 

Water, sea 

Acid, acetic 

Acid, nitric 

Acid, sulphuric 

Acid, muriatic (hydrochloric) 

Alcohol, pure 

Alcohol, proof 

Naphtha 

Petroleum 



1.000 
1.030 
1.062 
1.217 
1.841 
1.200 
0.792 
0.916 
0.848 
0.878 



0.036 
0.037 
0.038 
0.044 
0.067 
0.043 
0.029 
0.033 
0.031 
0.032 



8.33 
8.55 
8.78 
10.16 
15.48 
9.93 
6.70 
7.62 
7.00 
7.39 



WEIGHTS AND MEASURES 
Troy weight 

24 grains • • 1 pennyweight 

20 pennyweights 1 ounce 12 ounces 1 pound 

Used for weighing gold, silver and jewels. 

Apothecaries' weight 

20 grains 1 scruple 8 drams 1 ounce 

3 scruples 1 dram 12 ounces 1 pound 

Ounce and pound are the same as in Troy weight. 

Avoirdupois weight 

27 11/32 grains 1 dram 4 quarters. ... 1 hundredweight 

16 drams 1 ounce 2,000 pounds 1 short ton 

16 ounces 1 pound 2,240 pounds 1 long ton 

25 pounds 1 quarter 2,204 pounds .... 1 metric ton 

Dry measure 

2 pints 1 quart 4 pecks 1 bushel 

8 quarts 1 peck 36 bushels 1 chaldron 



USEFUL DATA 675 

Liquid measure 

4 gills 1 pint 413^ gallons 1 barrel 

2 pints 1 quart 2 barrels 1 hogshead 

4 quarts 1 gallon 2 hogsheads 1 pipe 

Long measure 

12 inches . 1 foot 40 rods 1 furlong 

3 feet 1 yard 8 furlongs 1 mile 

53^2 yards 1 rod 3 miles 1 league 

Cloth measure 

234 inches 1 nail 4 quarters 1 yard 

4 nails 1 quarter 

Square measure 

144 square inches. 1 square foot 40 square rods 1 rood 

9 square feet 1 square yard 4 roods 1 acre 

30J4 square yards. 1 square rod 640 acres 1 square mile 

Surveyor's measure 

7.92 inches 1 link 

25 links 1 rod 4 rods 1 chain 

10 square chains or 160 square rods 1 acre 

640 acres 1 square mile 

36 square miles (6 miles square) 1 township 

Cubic measure 

1,728 cubic inches. . 1 cubic foot 128 cubic feet. . . 1 cord (wood) 

27 cubic feet 1 cubic yard 40 cubic feet . . 1 ton (shipping) 

2,150.42 cubic inches 1 standard bushel 

231 cubic inches 1 U. S. standard gallon 

1 cubic foot about 4/5 of a bushel 

METRIC EQUIVALENTS 

Linear measure 

1 centimeter 0.3937 inch 1 inch 2.54 centimeters 

1 decimeter 3.937 inches 0.328 foot 

1 foot 3.048 decimeters 

1 yard 0.9144 meter 

1 meter 39.37 inches 1.0936 yards 

1 dekameter 1.9884 rods 1 rod 0.5029 dekameter 

1 kilometer 0.62137 mile 1 mile 1.6093 kilometers 



676 PRACTICAL TANNING 

Square measure 

square centimeter 0.1550 square inch 

square inch 6.452 square centimeters 

square decimeter 0.1076 square foot 

square foot 9.2903 square decimeters 

square meter 1.196 square yards 

square yard 0.8361 square meter 

hectare 2.47 acres 1 acre 0.4047 hectare 

square kilometer .0.386 square mile 

square mile 2.59 square kilometers 

Weights 

gram 0.03527 ounce 1 ounce 28.35 grams 

kilogram 2.2046 pounds 1 pound 0.4536 kilogram 

metric ton 1.1023 English tons 

English ton 0.9072 metric ton 

Volume 

cubic centimeter 0.061 cubic inch 

cubic inch 16.4 cubic centimeters 

cubic meter 35.29 cubic feet 

cubic foot 0.028 cubic meter 

cubic meter 1.308 cubic yards 

cubic yard 0.765 cubic meter 

Capacity 

liter 0.0353 cubic foot 1 cubic foot 28.32 liters 

liter 0.2642 gallon, U. S. 1 gallon 3.785 liters 

liter . . . .61.023 cubic inches 1 cubic inch 0.0164 liter 

Multiples for conversion of quantities 
To convert Multiply by 

Grains to grams . 065 

Ounces to grams 28 . 35 

Pounds to grams 453 . 6 

Pounds to kilograms . 45 

Hundredweights to kilograms 50 . 8 

Tons to kilograms 1016 . 

Grams to grains 15.4 

Grams to ounces . 35 

Kilograms to ounces 35 . 3 

Kilograms to pounds 2.2 

Kilograms to hundredweights . 02 

Kilograms to tons . 001 



USEFUL DATA 677 

Multiples for conversion of distances 

To convert Multiply by 

Inches to millimeters 25 . 4 

Inches to centimeters 2 . 54 

Feet to meters . 3048 

Yards to meters .9144 

Yards to kilometers . 0009 

Miles to kilometers 1.6 

Millimeters to inches . 04 

Centimeters to inches 0.4 

Meters to feet 3.3 

Meters to yards 1.1 

Kilometers to yards 1093 . 6 

Kilometers to miles . 62 

Multiples for conversion of capacities 
To convert Multiply by 

Cubic inches to cubic centimeters 16.39 

Cubic feet to cubic centimeters 28320 . 00 

Cubic yards to cubic meters . 7646 

Fluid ounces to centiliters 2. 958 

Gallons to liters 3 . 786 

Bushels to hectoliters . 3524 

Troy grains to milligrams 64 . 8 

Troy pounds to kilos . 373 

Avoirdupois pounds to kilos .4536 

Square feet to centimeters 929.00 

Square yards to meters 0.8361 

Liters to quarts, dry measure 0.908 

Liters to quarts, liquid measure 1 .0567 

Square meters to square yards 1 . 196 

Kiloliters to gallons 264 . 17 

Liters to gallons 0. 22 

APPROXIMATE METRIC EQUIVALENTS 

1 decimeter 4 inches 1 meter 1.1 yards 

1 liter 1.06 quarts liquid or 0.9 quart dry 

1 kilometer 5/8 of a mile 1 hektoliter 2^ bushels 

1 hectare 23^ acres 1 kilogram 2 1/5 pounds 

1 stere or cubic meter J4 of a cord 

1 metric ton 2,200 pounds 



678 PRACTICAL TANNING 

CAPACITY OF VATS IN GALLONS FOR EACH INCH 
IN DEPTH 

Circular in form 

5 feet diameter 12 . 24 

6 " " 17.76 

7 " " 23.63 

8 " " 31.50 

9 " " 39.38 

10 " " 48.56 

11 " " 59.24 

12 " * 70.50 

13 " " 82.74 

14 " " 95.96 

15 " " 110.16 

Cubic capacity of a circular vat is equal to the square of 
the radius multiplied by 3.1416, multiplied by the depth. 



5 feet square 


Square in form 


15.75 


6 " " 




22.31 


7 " " 




30.19 


8 " " 




40.03 


9 " " 




51.19 


" " 




62.34 



Sundry Calculations 

1 gallon contains 231 cubic inches. 

1 gallon of water weighs approximately 8^ pounds. 

8-J pounds multiplied by the specific gravity of a liquid 
equals the weight of a gallon of the liquid. 

Volume of a cube. — Multiply a side of a cube by itself 
and that product again by a side. If contents in gallons is 
desired, multiply the contents in cubic feet by 7.4805. 

Volume of a parallelopipedon. — Multiply length by breadth 
and that product again by depth. 

Volume of a cylinder. — Multiply the square of the diameter 
by 0.7854, and the product by the height. 



USEFUL DATA 679 

Volume of a cone. — Multiply the square of the diameter 
of the base by 0.7854, the product by the Derpendicular 
height, and divide by 3. 

Volume of o frustum of a cone. — Add together the 
square of the diameters of the greater and lesser sides and 
the product of the two diameters; multiply the sum bv 0.7854, 
and the product by the height; then divide the last product 
by 3. 

Example. — A tank is 5 feet across the base, 3 feet across 
the top, and 9 feet high ; get the volume : 

(5x5) + (3 x 3) + (5 x 3) = 49 
49 x 0.7854 = 38.4846 
38.4846 x 9 = 115.4538 cu. ft. 
3 

Volume of sphere. — Multiply the cube of the diameter by 
0.5236. This rule applies to kettles which as a rule may be 
considered one half of a sphere. 

Diameter and speed of pulleys. — 

D and d diameter of driving and driven pulleys 
R and r number of revolutions 
Then 

D =— * d= 5^-- R=—- -- DR 
R' r ' D' r d 

Heat, steam, evaporation and electricity 

Total heat of saturated steam (above $2° Fahrenheit}. — 
H = 1150.3 + 0.3745 (t — 212°) —0.000550 — 212°) 
where H is the total heat in B.t.u.'s above water at 32° 
Fahrenheit, and t is the temperature Fahrenheit. 

Latent heat of steam. — Obtained by subtracting from the 
total heat at any given temperature the heat of the liquid, or 
total heat above 32° Fahrenheit in water of the same 
temperature.. 

Heat required to generate 1 pound of steam from water at 
32° Fahrenheit is 1150.4 heat units. 

The heat unit (B.t.u. ), is the heat required to raise a 



680 PRACTICAL TANNING 

pound of water from 62° to 63° Fahrenheit, or 1/180 of the 
heat required to raise 1 pound of water from 32° to 212° 
Fahrenheit. 

French calorie = 3.968 B.t.u.'s. 
1 B.t.u. = 0.252 calorie. 

1 pound calorie — 9/5 B.t.u., = 0.4536 calorie. 
1 B.t.u. = 778 foot-pounds of energy. 
1 foot-pound = 1/778 = 0.0012852 B.t.u. 
1 horsepower = 33000 foot-pounds per minute = 2545 
B.t.u. per hour. 

Absolute zero is — 460° Fahrenheit. 

Evaporation in vacuum. — Approximate working figures : 
3 gallons per square foot heating surface per hour. 
1 pound of coal evaporates 8^ pounds of water — single 
effect. 

1 pound of coal evaporates 16 pounds of water — double 
effect. 

1 pound of coal evaporates 22 pounds of water — triple 
effect. 

1 pound of coal evaporates 28 pounds of water — quadruple 
effect. 

1 kilowatt hour = 

1.341 horsepower hours. 
2,655,200 foot-pounds. 
3,415 heat units. 

3.52 pounds of water evaporated from and at 212° Fah- 
renheit. 
22.77 pounds of water raised from 62° to 212° Fahren- 
heit. 
1 horsepower hour = 
0.7457 kilowatt hour. 
1,980,000 foot-pounds. 
2,546.5 heat units. 

2.62 pounds of water evaporated from and at 212° Fah- 
renheit. 
17.0 pounds of water raised from 62° Fahrenheit to 212° 
Fahrenheit. 



USEFUL DATA 



(581 



1 kilowatt = 

1.3410 horsepower. 
44,254 foot-pounds per minute. 
56.92 heat units per minute. 

3.52 pounds of water evaporated per hour from and at 
212° Fahrenheit. 
1 horsepower = 
0.7457 kilowatt. 
33,000 foot-pounds per minute. 
42.44 heat units per minute. 

2.62 pounds of water evaporated per hour from and at 
212° Fahrenheit. 



Boiling point of water at reduced pressure 



Inches of 


Temper- 
ature 


Temper- 
ature 


Inches of 


Temper- 


Temper- 


Mercury 


Degrees 

Fahrenheit 


Degrees 

Centigrade 


Mercury 


Degrees 

Fahrenheit 


Degrees 
Centigrade 





212 


100 


15 


179 


81.7 


1 


210 


98.9 


16 


176 


80 


2 


208 


97.8 


17 


173 


78 3 


3 


207 


97.2 


18 


169 


76 1 


4 


205 


96.1 


19 


165 


73.9 


5 


203 


95 


20 


161 


71 7 


6 


201 


93.9 


21 


157 


69.4 


7 


199 


92.8 


22 


152 


66 7 


8 


197 


91.7 


23 


147 


63.9 


9 


194 


90 


24 


140 


60 


10 


192 


88.9 


25 


133 


56 1 


11 


190 


87.8 


26 


125 


51.7 


12 


187 


86.1 


27 


114 


45.5 


13 


185 


85 


28 


100 


37.8 


14 


182 


83.4 


29 


77 


25 



682 



PRACTICAL TANNING 



Temperature of steam at various pressures 



Pounds per 
Square Inch 


Temper- 
ature 
Degrees 

Fahrenheit 


Temper- 
ature 
Degrees 
Centigrade 


Pounds per 
Square Inch 


Temper- 
ature 
Degrees 

Fahrenheit 


Temper- 
ature 
Degrees 
Centigrade 





212 


100 


45 


292 


144.4 


1 


215 


101.6 


50 


298 


147.7 


2 


219 


103.9 


55 


303 


150.5 


3 


222 


105.6 


60 


307 


152.7 


4 


224 


106.7 


65 


312 


155.5 


5 


227 


108.4 


70 


316 


157.7 


6 


230 


110 


75 


320 


160 


7 


232 


111.1 


80 


324 


162.2 


8 


235 


112.8 


85 


328 


164.4 


9 


237 


113.9 


90 


331 


166.1 


10 


239 


115 


95 


335 


168.3 


11 


242 


116.7 


100 


338 


170 


12 


244 


117.8 


105 


341 


171.6 


13 


246 


118.9 


110 


344 


173.3 


14 


248 


120 


115 


347 


175 


15 


250 


121.1 


120 


350 


176.6 


16 


252 


122.2 


125 


353 


178.3 


17 


253 


122.7 


130 


356 


180 


18 


255 


123.8 


135 


358 


181.1 


19 


257 


125 


140 


361 


182.7 


20 


259 


126.1 


145 


363 


183.8 


21 


260 


126.6 


150 


366 


185.5 


22 


262 


127.7 


155 


368 


186.6 


23 


264 


128.8 


160 


371 


188.3 


24 


265 


129.4 


165 


373 


189.4 


25 


267 


130.5 


170 


375 


190.5 


"26 


268 


131.1 


175 


377 


191.6 


27 


270 


132.2 


180 


379 


192.7 


28 


271 


132.7 


185 


382 


194.4 


29 


272 


133.3 


190 


384 


195.5 


30 


274 


134.4 


195 


386 


196.7 


35 


281 


138.3 


200 


388 


197.8 


40 


286 


141.1 









GLOSSARY OF TERMS USED IN TANNING AND RELATED 

INDUSTRIES 

Acid dye. A coal-tar color which is applied to leather without 
a mordant. 

Airing-off. Slightly drying the stock after application of 
finish. 

Annatto. A red dye of vegetable origin. 
_ Antiseptics. Preservatives which temporarily check fermenta- 
tion, such as dilute solution of formaldehyde, salt, etc. 

Arm-staking. A mechanical process employed to soften skins. 

Bacterial action. Effect produced through the agency of cer- 
tain bacteria. . 

Barkometer. A special hydrometer used in tanneries only, 
one degree of which is equivalent to 1.001 specific gravity. Then 
30° bk.= 1.030 specific gravity. 

Basic dye. A coal-tar color which requires the presence of 
tannic acid to fix it on the leather. 

Bate runs. Skins damaged by too violent action with bacterial 
bates. 

Bating. Treatment of skins with hen or pigeon manure or 
other bacterial agents, to neutralize lime and render them flaccid. 
Bating also opens the pores of the skin, and so assists subsequent 
treatment. 

Baume. An arbitrary scale for determining the density of a 
liquid. 

Beam. A rounded support for holding hides or skins during 
unhairing or fleshing by hand. 

Beam-house. That part of the tannery where the hides are 
treated previous to tanning. 

Bettered. Strengthened. 

Bleaching. The removal of part of the surface tan to pro- 
duce a light-colored stock. 

Boarding. Producing a false grain on leather. 

Bottoming. Filling a leather and giving a suitable foundation 
for a dye. 

Buffing. Removal of the grain or flesh of leather by mechani- 
cal means to eliminate defects or obtain a level surface. 

Butt. The best part of the skin, or hide directly over the 
rump. 

Cabretta. A cross between a goat and a sheep. 

Casein. A product obtained from the souring of milk. 

683 



684 GLOSSARY OF TERMS 

Castor leather. A kind of glove leather. 

Centigrade. Boiling point of water, 100 degrees; freezing 
point, degrees. 

Chamois. Leather produced by incorporation of an oxidizable 
oil, such as cod-liver oil. 

Cod oil. Newfoundland cod-liver oil. 

Colon. The large gut of an animal. 

Copperas. Iron sulphate; ferrous sulphate. 

Currying. Introducing grease into leather and giving it any 
desired finish. 

Deacons. Small calfskins. 

De-greasing. Removal of grease either by solvents, by saponi- 
fication, or by pressing. 

De-hairing. The chemical removal of hair from hides; also 
a general term in removing hair. 

De-liming. Soaking skins in a weak acid or other solution 
to remove lime. 

Dermiforma. An artificial bate. 

De-tanning. Extracting vegetable tanning materials by means 
of borax or soda to prepare skins for re-tanning with another 
agent, such as chrome. 

Depilation. The process following the soaking of hides, such 
as immersing them in an infusion of lime, which loosens the 
hair without injuring the skin. 

Depleting action. Any action which tends to loosen the hair 
and epidermis. 

Dermis. The true skin or that part from which leather is 
produced. 

Direct dye. A coal-tar color which may be applied to leather 
without a mordant. 

Disinfectant. A purifier ; a compound which kills both bacteria 
and their spores. 

Drench. A mixture of bran and water which has been al- 
lowed N to ferment, and so contains acetic and lactic acids. It 
neutralizes and removes lime, and has a plumping effect. 

Drum. An apparatus in which hides or skins are tumbled to 
aid in tanning, coloring, fat-liquoring, and stuffing. 

Dubbin. A mixture of oil and tallow for stuffing leather. 

Effect. Part of a vacuum apparatus used in evaporating tan- 
ning extracts or other solutions. 

Embossing. Producing an artificial grain on leather. 

Enzyme action. The result of unorganized ferment. 

Epidermis. The external layer of the skin. 

Fahrenheit. Boiling point of water, 212 degrees; freezing 
point, 32 degrees. 

Fat-liquor. An emulsion of soap and oil; a mild alkali such 
as borax and oil, or a sulphonated oil, in which skins are worked 
after tanning and washing. 



GLOSSARY OF TERMS 685 

Filling leather. Introduction of substance to give weight 
and body. 

Fleshing. Removal with a knife of portions of flesh, etc., 
which adhere to the hide. Fleshings contain considerable fat and 
gelatine, which are recovered. 

Fluffing. Producing a soft effect on grain or flesh side of 
leathers. 

French chalk. Talc, or magnesium silicate. 

Frizzing. Removing the outer grain of skins on a beam after 
long lime treatment — 30 or 40 days. 

Furs. Skins tanned without removal of the hair. 

Fustic. A yellow vegetable dyestuff. 

Glassing. Producing a bright finish on the grain by means of 
a glass slicker or roll. 

Grain. That portion of the hide just under the epidermis. ^ 

Hair-slip. An effect produced when the grain of a pelt is 
partly decomposed. 

Handler. A pit containing vegetable tanning solutions in 
which hides are suspended. 

Hauling. Taking hides out of lime solution. 

Hematin. An oxidized logwood. 

Hides (green). Raw hides from the butcher. 

Hides (split). A hide that is split into two layers. The 
grain layer is used for one purpose, while the flesh split may 
have another application. 

Horsing-up. Placing the hides or skins over a horse to 
drain. 

Irish moss. Kelp or seaweed extract. 

Iron in tanning operations. No iron should come in contact 
with hides or solutions during vegetable tanning, as iron sulphate 
is formed, which stains the finished goods. Wood or brass may 
be used. 

Jacking. Stretching the stock on boards or frames and hold- 
ing it in position by means of tacks. 

Kid. A small goat. 

Kip. A pelt having a weight between calf and a light hide. 

Kiss spot. Light-covered spots which appear on vegetable- 
tanned leather when two hides have touched during the early 
stages of tanning. 

Knee-stake. A mechanical device used especially for soften- 
ing alum-tanned glove leather. 

Lamb. A young sheep. 

Layaways. Pits in which heavy hides receive their first 
tannage. 

Logwood. A vegetable dyestuff used for producing a black 
color. 

Mocha leather. A kind of glove leather. 

Mordant. A material used to fix a dyestuff. 



686 GLOSSARY OF TERMS 

Muriatic acid. Hydrochloric acid. 

Oropon. A patented bate. 

Osage orange. A yellow vegetable dyestuff. 

Paddle. An apparatus used in bating, tanning and coloring 
skins. 

Patent leather. A leather with a bright varnish finish. 

Pelts. Skins in the hair as received by the tanner. 

Perch. A mechanical device used for softening skins. 

Perching. Softening and stretching leather with a moon- 
knife or on a staking machine. 

Pickling. Treating de-limed, bated, or drenched stock with 
salt and sulphuric acid. 

Plumping. Softening and swelling of hide fibers which con- 
tain little water. Plumping follows the removal of salt on treat- 
ment with dilute acids and alkalies. 

Plunging. Stirring up the liquors. 

Puerine. An artificial bate. 

Puering. Bating, but using dog manure in place of hen 
manure; a term also employed when other bacterial agents are 
used. 

Re-staking. Further softening of leather; usually done on 
the dry stock. 

Re-tan. To tan again. 

Saddening agent. The addition of a substance during dyeing 
to produce a duller shade. 

Sal-ammoniac. Ammonium chloride. 

Sal soda. Sodium carbonate containing 12 molecules of water 
of crystallization. 

Salts of tartar. Potassium carbonate. 

Salted skins. Those cured with salt. 

Sammie. Half dry. 

Setting-out. Removing excess of liquid and eliminating 
wrinkles. 

Shearlings. Sheepskins which have been sheared just prior 
to killing of t,he animal. 

Side leather. Leather made from hides that have been split 
into sides. 

Sig. A seasoning made of adhesive compounds (see section 
on harness leather). 

Skiver. The grain side of a split sheepskin. 

Skiving. Removing superfluous flesh from the flesh side of 
the leather, or separating the grain. 

Slicking. Setting-out the wet leather by means of a slicker. 

Slunk. The skin from an unborn calf. 

Snuffing. A light buffing on the grain side. 

Soaking. Washing hides with water to remove dirt, blood, 
and salt, previous to liming. 



GLOSSARY OF TERMS 687 

Sod oil. _A product obtained by neutralizing the washing 
from chamois leathers. 

Spew or spue. A white exudation which sometimes appears 
on the grain of finished leather. 

Splits. The hide from which the grain has been removed. 

Stoning. ^ Smoothing down leather with a stone. 

Stoning-jack. A machine which is provided with a stone, 
and is used for smoothing out leathers. 

Striker. A substance applied to leather to get the color. 

Struck through. When the tanning agent has penetrated 
through the hide it is struck through. 

Sumac. The leaf of a tree largely grown in Sicily, and con- 
taining up to 30% tannin. Prices are quoted f. o. b. Palermo, 
per hundredweight, Yocum's test. 

Surficial. Pertaining to the surface of the hide or leather. 

Sweating. A natural process of putrefaction brought about 
by storing hides in a warm and damp atmosphere, so that bac- 
teria grow and loosen the hair. 

Talc. Magnesium silicate or French chalk. 

Tan. Any material which will prevent putrefaction of hide 
substance. 

Tannage. A process of converting hide substance into leather. 

Tannate. Such as titanium tannate, a yellowish shade, on 
which bottom all shades of tan, brown, green, blue, and maroon 
can be obtained. 

Tannic acid. The active principle in manv vegetable materials, 
which has the power of converting hide substance into leather.' 

Tanning:. Treating prepared skins with an infusion containing 
Tannic acid. 

Tartar emetic. Antimony-potassium tartrate. 

Tawing. Treating skins with compounds of aluminum. 

Toggle. Fastening hides together by means of special hooks. 

Trimmings. The useless parts of hides, used for glue manu- 
facture. 

Twaddell. An arbitrary scale for determining the density of 
a liquid. J 

Unhairing. De-hairing: the mechanical removal of loosened 
hair after the action of the depilatory. 

Wallaby. A small animal of the kangaroo family. 

Weighting leather. Adding some material to produce weig-ht 
and fullness, sometimes termed adulterating. 

Welting. A strong thin leather cut into strips. 

Welting-stock That portion of a hide not suitable for sole 
leather and used for making welts. 



INDEX 



(For references not given under this head see Glossary of Terms 
on pages 683 to 687 inclusive.) 



Acetyl number, 653 
Acid colors, 354, 367 

hemlock, 270 
Acidity of liquors, determination 

of, 619 
Activated sludge, 667 
Adipose tissue, 51 
Adjective dyes, 352 
Adler, Geo. W., cited, 171 
Aged oil, 342 
Agras, 28 
Algarrobilla, 555 
Algin, 497 
Algoabays, 27 
Alizarine colors, 355 
Alligator skin, grain of, 36 
Alum and chrome tanning, 169 
tannage, 138, 229 
snake skins, 152 
tanned lace, 136 
leather, coloring, 361 
Alumina-pickled grain, 177 
Aluminum bisulphite reduction, 
194 
sulphate, analysis of, 601 
and salt pickle, splitting out 
of, 132 
Amend, O. P., cited, 114 
American Leather Chemists' As- 
sociation, official method of 
analyzing vegetable tannins, 
612 
Ammonia, simple test for, 662 
Ammonium butyrate in de-liming, 
115 
chloride, simple test for, 660 

in de-liming, 114 
phosphate in de-liming, 116 
Amritsars, 28 

Analysis of vegetable tannin ma- 
terials, 612 
Analytical methods, 585 
A-naphthol, 563 
Anglo-American hides, 18 
Antique leather, 380 
Apothecaries' weight, 674 
Arabian goatskins, 27 
Arazym, 86 

on goatskins, 106 
Arm-board, 255 
Arsenical limes, 92 



Arsenic sulphide, 85, 91 

analysis of, 593 
Artificial dyestuffs, 354 

coloring with, 376 

leather, 578' 
Autoclave system, 532 
Automobile leather, 318, 336 
Avoirdupois weight, 674 

Backer, 10 

Bag leather, 318, 322 

coloring, 408 
Banana liquid, 499 
Bark mill, 527 
mimosa, 555 _ 
wattle (acacia), 556 
Barks, 542 
Basic colors, 354 
dyestuffs, 354 

coloring with, 364 
Bate, C. T., 116 

beam-stone, 117 
Bating, 119 

with dog dung, 121 

glucose, sulphur and yeast, 

121 
hen manure, 123 
molasses, 120 
Oropon, 125 
Bavarian hides, 19 
Bayonet scabbards, 134 
Beam, 86 

knife, 80 
Beam-house, 100 

in goatskin tannery, 100 
work, 90 
Belting, driving efficiency of 
grain and flesh sides, 317 
leather, 292, 293 

characteristics of, 292 
chrome, 183 
coloring, 408 
drum tannage, 289 
manufacturing process for, 

295 
practical considerations, 298 
raw materials for, 293 
tanning, 301 
tanning agent, 296 
Belt-knife splitting machine, 131 
Belt-pins, 134 



689 



€90 



INDEX 



Bend, 272 

Black gambier, 554 

glazed finish, 455 
Blacking, 412 

machine, 386 

varnish, 484 
Blacks on chrome leather, 359 
Bleaching, 141, 238, 279, 305 

machine, 281 
Bleach pits, 280 
Blood, 492 

albumen, 492 
analysis of, 656 
B-naphthol, 563 
Boarding, 453 

machine, 325 
Boiling oil, 343 

point of water, 681 
Bokharas, 26 

Bones, disinfection of, 38 
Borax in soaks, 64 

neutralizing with, 172 

simple test for, 662 
Boric acid in de-liming, 111 
Bot-fly, 14 

Bower glazing machine, 460 
Box finish, 471 _ 
Bran in drenching, 117 
Brand marks, 2 
Branding, 17 
Brazil wood, 353 
Broad flesher, 81 
Bronze dyeing, 381 
Brown shades, 398 
Brush dyeing, 356 

killing, 520 
Brushing machine, 288 
Buckskins, chrome, 196 

tanning, 154 
Indian method, 155 

white, 155 
Buenos Aires, 18 
Buffing,_ 450 
machine, 146 
room, 459 
wheel, 148 
Bull hides, 17 
Button lac, 499 
Butyric acid, 61 
in de-liming, 114 

Calcium chloride, 96 

polysulphide, 91" 

sulphydrate, 86 
Calf, Russia, 238 
Calfskin, cross-section of, 49 

fancy leather, 258 

glove leather, 201 

leather, 233 

'white, 145 



mitten leather, 201 
quebracho-tanned, 233 
Calfskins, 19 
soaking, 62 
Capacity of vats, 678 
Capes, 27 
Capetowns, 27 

Carbonic acid in de-liming, 112 
Casablancas, 27 
Case leather, 322 
Casein, 495 

Castor leather, imitation of, 144 
liming, 105 
oil soap, 441 
Caustic soda, 85 
in depilation, 85 
in soaks, 61 
production of, 85 
simple test for, 660 
Chamois, bleaching, 141 
coloring, 388 
leather, 140 
Checking machine, 99 
Chemical Foundation, 558 
soaks, 61 
tests, 659 
Chestnut bark, 545 
tannage, 229, 283 
tree, 538 
wood, 538 
China goatskins, black on, 516 
Chinese blue, 343 

goatskins, 28 
Chipper, disc, 529 

hog, 528 
Chocolate shades, 402 
Chrome alum, dissolving, 193 
bag, coloring, 408 
belt, coloring, 408 
calfskins, seasoning for, 470 
goatskins, finish for, 472 
harness, blacking, 416 
finishing, 417 
leather, 181 
kangaroo black, 405 
lace leather, 201 

stuffing, 445 
leather, black, 403 
difference in, 175 
oiling, 442 

sulphonated oil on, 440 
liquor, analysis of, 603 

one-bath, analysis of, 608 
mitten leather, 178 
patent leather, 187 
process for acid pickled stock 
177 
one-bath, 159 
two-bath, 158 
residues, recovery of, 195. 



INDEX 



691 



sheepskins, blacking, 372 

flesh-finished, 371 
side glove leather, 178 
leathers, black, 409 
dyeing, 409 
fat-liquor for, 428 
finish for, 474 
sole leather, 178 
strap leather, 183 
tannage, 158 
suggestions on, 173 
new two-bath process, 171 
tanned belt leather, 183 
buckskin, 196 
calfskins, black, 389 
coloring, 390, 391 
dyes for, 359 
fat-liquor for, 424 
goatskins, black, 402 

dyeing, 395 
kangaroo, fat-liquor for, 427 
leather, analysis of, 635 

dyeing, 358 
sheepskins, coloring, 362 
• fat-liquor for, 422 
finishing, 454 
side leather, 176 
wax calf, 207 
tanning, theory of, 198 
velvet leather, 187 
Clarification of extracts, 533 
Classification of dyestuffs, 352 
Clearing of grain, 398, 473 
Cloth measure, 675 
Cloud test, 652 
Coal-tar bates, 116 
Coating leathers, 581 
Coats, tanning of, 522 
Cod-liver oil, simple test for, 660 
Cold sweat, 71 
Cold test, 651 
Collodion, 499 
varnish, 380 
Color formulas, 360 

on stuffed leather, 330 
Colorado steers, 17 
Colored sheepskins, seasoning 

for, 458 
Coloring after fat-liquoring, 370 

goatskins, 357 
Combination process for depila- 
tion, 101 
tannage, 227, 247, 260 
Concentration of extracts, 535 
Condensation products, 558 
Cone mill, 526 

volume of, 679 
Connective tissue, 50 
Conservation of skin substance, 

52 
Conversion multiples, 676 



Cooper-Hewitt lamp, 347 
Corium, 48, 51 
Country hides, 17 
Cowhide, 17 

cross-section of, 50 

grain of, 16 
Cows, spready, 17 
Cropping, 275 

Cross-section of calfskin, 49, 51 
Crystal sulphide, 85 
Cuba wood, 353 
Cube, volume of, 678 
Cubic measure, 675 
Curing, 10, 22 
Currier's knife, 308 
Currying, 306 
Cutch, 353 
Cuticle, 48 
Cutis, 48 
Cut-throats, 3 
Cyco powder, 11 
Cylinder, volume of, 678 

Daccas, 28 

Dampening, 449 
Dark tan shades, 401 
Daub coat, 343 
Deacons, 19 

De-greasing by vacuum od pro- 
cess, 68 

fluid, gargoyle, 130 

pigskins, 68 

in the Krouse process, 68 
De-hairing, use of term, 86 
De-liming, 110 

ammonium butyrate, 115 

ammonium chloride, 114 

ammonium phosphate, 116 

boric acid, 111 

butyric acid, 114 

carbonic acid, 112 

hydrochloric acid, 111 

lactic acid, 112 

sodium bisulphite, 111, 116 

sodium dichromate, 115 

sulphuric acid, 111 

sulphurous acid, 111 

test, 111, 599 

zinc sulphate, 116 
Dennis Co., Martin, 116 

puerine, 126 
Density tables, 673 
Depilating glove leather, 103 
Depilation, 71 

methods of, 87 
Depilatories, patented, 104 
Depilatory compound for wool 
skins, 101 

paints, 104 
Derma, 48 
Dermiforma, 123 



692 



INDEX 



Dihydroxybenzene, 560 
Direct black, 403 ■■ 

colors, 355 

dyeing with, 367 

leather blacks, 391 
Disc chipper, 529 
Disinfection of bones, 38 

hides, 36 

railroad cars, 42 
Divi-divi, 555 
Dog dung, 121 
Dongola tannage, 236 
Dope splits, 578 
Drench, mild fermented, 118 
Drenching, 116 

with bran, 117 
Dressings, 482 

waterproof, 485 
Dried blood, simple test for, 659 

hides, 1 

skins, soaking of, 65 
Driers, 345 
Driving surface, 292 
Drum, 56 

dyeing, 356 

heads, 134 

tannage, 289 
Drumming with sumac, 239 
Dry hides, 2, 58 

measure, 674 

salted hides, 1 
skins, soaking, 66 

sheepskins, 65 

skins, soaking, 62, 63 
Drying, 306, 448 

loft, 286 
Dry-room, 450 
Dry-salted hides, 58 
Dull finish, 458 
Dyeing, 352 

leather, 352 

notes on, 400 

vegetable-tanned leather, 356 
Dyes, simple test for, 659 
Dyestuffs, acid, 354 

alizarine, 355 

basic, 354 

classification of, 352 

direct, 355 

dissolving, 355 

Egg albumen, 493 

Egg-yolk, 435 

analysis of, 657 

simple test for, 661 
Ehrenreich, Alfred, cited, 574 
Electric tanning, 567 
Electrical units, 680 
Embossed sheepskins, finish for, 
460 



Embossing, 453 

machine, 338 

press, 337, 339 
Epithelium, 48 
Eureka bark mill, 527 
Evaporation, 679 
Evaporator and dryer, combined, 

619 
Extract, analysis of, 614 

wheels, 278 
Extracting, 278 
Extracts, clarification of, 533, 535 

Fancy colors, 379 

leather, 258 
Fat-liquor, applying, 428 

formulas, 431 
Fat-liquoring, 419 

process, 421 
Fats, 419 
Fatty resist, 380 
Fell-beater, 9 

cutter, 9 
Ferrous sulphate, simple test for, 

660 
Fig soap, 436 

Fine hair, inspection for, 95 
Finishing processes, 447 

materials, 491 

sole leather, 287 
Fitz-Henry machine, 308 
Flash point, 652 
Flat bed glazing machine, 461 
Flaying, 4 
Flesher, 81 

monitor, 81 
Fleshers, sheepskin, 143 
Fleshing, 60 

knife, spring style, 81 

machine, 60 
automatic roller, 82 
Flexible splits, 250 
Flint hides, 2 
Floorsman, 9 
Flour paste, 488 

simple test for, 661 
Flume, 539 

terminus, 540 
Fly-blow, 34 

Foerderer, Robert, cited, 433 . 
Formaldehyde, 53 

analysis of, 603 

antiseptic action of, 53 

raw stock, 70 

tannage, 147 

tanning with, 156 
Formic acid, 59 

analysis of, 657 

and salt pickle, 128 

in soaks, 59 



INDEX 



693 



Fox, red-haired, 521 
Fresh hides, 56 

skins, soaking of, t>3 
Frigorificos, 18 
Frustum of a cone, volume of, 

679 
Full grain finish, 416 
Fulling stocks, 59 
Furrol dye, on furs, 519 
Furs, 501 

acid color on, 517 

alum process on, 523 

alum tannage, 506 

black on, 519 

chlorinating of, 517 

chromate colors on, 518 

chrome-tanned, 513 

deodorizing, 512 

dyeing, 517 

dyeing black, 521 

formaldehyde tannage, 504 

furrol dyes on, 519 

mordanting, 520 

oil process, 511 

soaking, 69 

softening, 524 

tanning, 501 

vegetable tannage, 505 
Fustic, 353 

bottom, 368 

mordant, 365 

Gall nuts, 552 
Gambier, 554 

liquor, 139 

mordant, 365, 397 

tannage, 234, 240 . 
Gargoyle de-greasing fluid, 129 
Gelatine, 493, 494 
German goatskins, 25 
Glazed kid, 161 
Glazing, 452 

machine, 460 
Glossary of terms, 683-687 
Glove leather, chrome, 178 

calfskin, 201 

depilating, 103 

kid, 147 

process for, 166 
Glucose, determination of, 625 

simple test for, 660 

sulphur and yeast, bating with, 
121 

tables, 626 
Glue, 493, 494 

stock, disinfection of, 38 
Goatskins, 21, 65 , 

arazym on, 106 

black, 402 

buffing, 459 



coloring, 357 

finish for, 472 

glazing, 462 

grain on, 22 

liming, 99 

perching, 458 

soaking, 65 

sorting, 464 

staking, 457 

tannery, beam-house in, 100 

tan-room, 162 

warehouse, 24 
Goodyear welting, 321 

welts, 250 
Grain, clearing, 398 
Grasser, George, cited, 560 
Grease, recovery of, 130 

analysis of, 642 
Greasy skins, washing of, 511 
Green hides, 1 
Green-salted hides, 1, 57 

sheepskins, 65 

skins, soaking, 62 
Grub allowance, 15 
Grubs, 14 

Gum arabic, simple test for, 659 
Gunmetal finish, 471 

Hair, disinfection of, 40 

removed by sodium sulphide, 83 
Hairsheaths, 50 
Hairskins, alum tannage, 515 

soaking, 69 

tanning, 509 . 
Hand fleshing, 94 

seasoning, 416 

stuffing, 309 
Handlers, 302 
Harness blacking, 485 

leather, 318, 329 
chrome, 181 
Heat, 679 

units of, 680 
Heaver, 12 

Heavy rolling jack, 316 
Hematin, 353 
Hemlock bark, 546 

leather, acid, 270 
non-acid, 269 

tannage, 226 
Hen manure, 123 
Herrars, 28 
Hide structure, 48 

substance, 596 

conservation of, 52 
Hides, 1 

Anglo-American, 18 

Bavarian, 19 

bull, 17 

country, 17 



694 



INDEX 



cow, 17 

disinfection of, 36 

dried, 1 

dry, 58 

dry-salted, 1, 2, 58 

fresh, 56 

green, 1 

green-salted, 1, 57 

increase in weight from liming, 
76 

inspection of, 12 

liming, 87 

loss in weight during liming, 78 

market, 56 

packer, 3 

raw, 134 

selection, 16 

South American, 18 

spready, 16 

straight, 18 

Swiss, 19 

taking-up, 12 

washing, 57 
Hog chipper, 528 
Hogskins, 29 
Horsehides, 19 

fronts, 20 
Hot stuffing, 314 
Hou, T. P., cited, 214 
Human skin, grain of, 36 
Hyaline, 50 

Hydrochloric acid and calcium 
chloride pickle, 128 

in de-liming, 111 
Hydrated lime, 73 
Hydroquinone, 560 
Hydrosulphite, 335 

Imitation castor, 144 

India goatskins, 28 
tanned skins, 28 

coloring, 383 

finish for, 465 

re-tanning, 383 
Indicators, 664 
Indigo, 353 
Inspection for fine hairs, 95 

of hides, 12 
Intestinal leather, 208 
Iodine number, 653 
Irish moss, 497 
Iron liquor, analysis of, 658 
tannage, 214 

patents on, 216, 222 

research in, 215 
Ironing, 452 
Isinglass, 495 
Italian goatskins, 25 



Jackson, D. D., cited, 214 

Japan wood, 353 

Kaffirs, 27 
Kangaroo black, 405 

leather, finish for, 474 

skin, 67 

grain of, 35 
soaking, 67 

vegetable-tanned, 240 
Kaolin, acid-washed, 620 
Keratin, 49 
Kid glove leather, 147 

skin, grain of, 35 
Kids, sheep, 32 
Killing, brush, 520 

with caustic, 519 
lime, 519 
soda, 519 
Kinney, C. B., cited, 414 
Kips, 1, 18, 19 

soaking, 62 

sulphide process for, 95 
Kjeldahl method, 596 
Knee-staker, 150 
Knocker, 3 
Kosher, 3 
Krouse process, 68 
Kushtias, 28 

Lace leather, 134 

alum-tanned, 136 

chrome, 201 

oil-tanned, 135 
Lacterine, 495 
Lactic acid, analysis of, 644 

in de-liming, 112 

simple test for, 663 
Lamb, M. C, cited, 102, 113 
Lambskin, dyeing of, 521 

grain of, 35 
Lampblack, 343 
Lateral stiffness, 292 
Latigo leather, 135 
Layaways, 303 
Layer-pit, 274 
Leaching, 531 
Leather, color on stuffed, 330 

dyeing, 352 

for organ pipes, 212, 569 

for player-pianos, 570 

intestinal, 208 

lace, 134 

latigo, 135 

oil-tanned, 140 

picker, 138 

white calfskin, 145 
Legger, 4 



INDEX 



695 



Leidgen unhairing machine, 93 

unhairing on, 93 
Levant grain, 467 

seal, 251 
Lice, 34 
Ligl-rt shades, 399 

dyeing, 366 
Light tan shades, 401 
Lime, 72 

analysis of, 590 

and arsenic, 97 
sulphide, 88 

liquors, analysis of, 594 

plunger, 79 

putrid, 74 

simple test for, 659 

splitting out of, 131 
Liming, 72 

after removal of wool, 105 

calfskins, 96 

for castor leather, 105 

for mocha leather, 105 

for sole leather, 94 

goatskins, 99 

hides, 87 

thin grain, 92 
Linseed meal, simple test for, 659 

oil, 341 
Liquefying bacteria, 52 
Liquid measure, 675 
Liquor, analysis of, 618 
Lissom, 498 
Litharge, 343 
Loading wheel, 282 
Logwood, 353 

bottom, 368 
Long measure, 675 
Lubricating oils, analysis of, 648 

Machine finishing, 416 

Madras, 28 
Mangrove bark, 552 
Marbled effects, 379 

suede, 413 
Market hides, 56 
Marrakesh, 27 
Measuring, 453 

machine, 463 
Mechanical hoist, 273 

transfer, 272 
Metaderos, 18 
Metallic luster, 381 
'Methods of depilation, 87 
Metric equivalents, 675 
Mild fermented drench, 118 
Milk albumen, 495 
Mill coloring, 414 
Mimosa bark, 555 
Mineral acids, simple test for, 662 

dyestuffs, 354 



Mitten leather, calfskin, 201 

chrome, 178 
Mocha leather, liming of, 105 
Mochas, 27 

Moellons, analysis of, 641 
Mogadors, 27 
Molasses, bating with, 120 
Moniter flesher, 81 
Montevideos, 18 
Moon-knife, 232 
Mordant, fustic, 365 

gambier, 365, 397 

osage orange, 365 

sumac, 365, 397 
Mordanting furs, 520 
Morocco finish, 466 
Munson and Walker's table, 627- 

633 
Myrabolans, 555 

Naphtha, 342 

Napthalene condensations, 562 

Native steers, 16 

Natural dyestuffs, 352 

coloring with, 401 
Neradol, 558 
Neutralizing chrome skins, 167 

with borax, 172 
Nihoul, E., cited, 563 
Nitrocellulose, 499 
Non-acid hemlock, 269 
North African goatskins, 26 

Oak bark, 545 

leather, 265 

wood, 541 
Official method of tannin analysis, 

613 
Oil, boiling of, 343 

grain, 477 

process for furs, 511 

tanned leather, 140 
Oiling, 306 

leather, 426 
Oils, 419 

analysis of, 648 
One-bath chrome, 177 

liquor, analysis of, 608 

on pickled sheepskins, 166 

process, 159, 197 
Ooze calf, notes on, 394 

coloring, 405 

leather, 387 
Organ leather, 212, 569 
Oropon, 107, 124 
Osage orange, 353 

mordant, 365 
Oudhs, 28 
Ox-blood shades, 369, 377, 402 



696 



INDEX 



Packer hides, 3 

Paddle dyeing, 357 

soaking, 61 

vat, tanning in, 169 
Paints, depilatory, 104 
Palmetto, 556 

Parallopipedon, volume of, 678 
Parchment, 134 

like leather, 211 
Patent leather, 341 

chrome, 187 

drying of, 347 

shoe tipping, 260 

tipping, 482 
Patented depilatories, 104 
Patents for iron tannage, 216-222 
Patna skins, 28 
Peach wood, 353 
Pelts, 1 

classification of, 1 
Perching, 458 
Pernambucos, 29 
Petropaul goat, 26 
Phenol, simple test for, 663 
Phosphine dyestuffs, 367 
Picker leather, 138 
Pickle, analysis of, 602 
Pickled sheepskins, one-bath 
chrome on, 166 

two-bath chrome on, 163 
Pickling, 127 
Picric acid, 561 
Pigment finish, 414 
Pigskins, 67 

de-greasing, 68 

.dyeing, 412 

soaking, -67 

tanning, 255 

washing, 68 

white, 151 
Pin mill, 56 
Pipes, weight of, 670 
Player-piano leather, 570 
Plumping effect of lime, 91 

sulphide, 91 
Plunged up, 79 
Plunger, 79 
Pneumatic fleshing machine, 60 

pouches, 570 
Popular shades, dyeing, 368 
Porpoise leather, 574, 577 
Potash soap, 436, 441 
Powder, cyco, 11 
Press, embossing, 339 
Pressing grease from pickled 

skins, 128 
Priest, G. W., cited, 341 
Proctor dryer, 447, 448, 449 
Prussian blue, 343 
Puerine, 126 



Puerine D, 127 
Puering, 119 
Pulleys, speed of, 679 
Punjabs, 28 
Putrid lime, 74 

soaks, 60 
Putting-out machine, 132 
Pyro tan, 140 
Pyrocatechol, 560 
Pyrogallol, 560 
Pyroxylin, 499, 578 

solvents for, 578 

Quebracho, 547 

tanned sheepskins, 230 
Quicklime, 72 
Quinone, 563 

preparation of, 564 
Quirin press, 277 

Rabbinical law, 3 

Raccoon, 521 

Rapid sole leather tannage, 281 

tanning for sole leather, 263 
process, 263 
Raw hide, 134 
Recovered grease, 130 
Red-haired fox, 521 
Reel, 87 

Report form, official,. 646 
Resorcin, 560 
Re-tanning, 207 

with gambier, 247 

with quebracho, 239 
River Plate hides, 18 
Robes, tanning of, 522 
Rogers' shark-liver oil process, 

142 
Rohm's bate, 124 
Roller leather, 231 
Rolling, 452 

jack, 285, 316 
Rosenthal, Geo. D., cited, 51 
Rough leathers, finish, 480 
Rumper, 9 
Russia calf, 238 

chrome leather, notes on, 394 

goatskins, 26 

Saddle-tops, 134 

Saladeros, 18 

Salt, analysis of, 600 

pickle and aluminum, sulphate, 
splitting out of, 132 

simple test for, 660 

stains, 3 
Salting hides, 54 
Sampling tanning materials, 620 
Schlegel, Henry, cited, 115 



INDEX 



697 



Schultz, Augustus, cited, 158 
Schultz process, 158 
Scouring, 307 
Seal, imitation of, 522 

Levant grain, 251 

rabbit, 522 

walrus grain, 252 
Sealskins, dyeing, 411 

grain of, 36 

tanning, 250 
Seasoning, 451, 458 

machine, 386 
Semi-chrome leather, 203 
Serial table machine, 313 
Set, 79 

Setting-out, 284, 447 
Seymour-Jones, cited, 568 
Shark-liver oil process, Rogers, 
142 
tannage, 135 

skin leather, 574 

treatment of, 576 
Sharks, catching, 575 
Shaving machine, 164 
Sheep kids, 32 
Sheepskins, 30 

de-greasing, 463 

fleshers, 143 

grain of, 34 

one-bath chrome on, 166 

quebracho-tanned, 230 

soaking, 63 

two-bath chrome on, 163 

vegetable-tanned, 225 

white chrome-tanned, 168 
Sheep ticks, 33 
Shellac, 498 

simple test for, 662 
Sheridan press, 337 
Side leather, chrome-tanned, 176 

dyeing, 409 

vegetable-tanned, 242 

white, 185 
Sides, 9 

sulphide process for, 95 
Sigs for greasy leather, 486 
Simple chemical tests, 659 
Skins, 1 

India-tanned, 28 

Patna, 28 
Skinning, 4 
Skivers, 230 

finishing, 468 

for player-pianos, 570 
Skiving, 308 
Skunk, imitation of, 521 
Slaked lime, 90 
Slicker, 232 

Small, F. H., cited, 292 
Smooth plate press, 339 



Snakeskins, 152 

alum tannage, 152 

tanning, 257 
Snuffing machine, 146 
Soaking, 56 

calfskins, 62 

dried skins, 65 

dry-salted skins, 66 

dry skins, 62, 63 

fresh skins, 63 

furs, 69 

goatskins, 65 

green-salted skins, 62 

hairskins, 69 

kangaroo skin, 67 

kips, 62 

paddle, 61 

pigskins, 67 

sheepskins, 63 

Soaks, analysis of, 589 

borax in, 64 

butyric acid in, 61 

caustic soda in, 61 

chemical, 61 

putrid, 60 

sodium bisulphite in, 64 
Soap, analysis of, 647 

black, 488 

castor-oil, 441 

fig, 436 

potash, 436, 441 

simple tests for, 663 
Soda, simple test for, 663 
Sodium bisulphate and acid col- 
ors, 367 

bisulphite in de-liming, 111, 116 
in soaks, 64, 67 

dichromate in de-liming, 115 

hydroxide in soaks, 61 

sulphide, 82 
analysis of, 591 
and calcium chloride, 96 
as a depilatory agent, 82 
preparation of, 85 
process, 89 

thiosulphate, simple test for, 
661 
Softening furs, 524 
Sole leather, 263 

chrome, 178 

drum tannage, 289 

jack, 268 

liming of, 94 

sulphonated oil on, 441 
Soluble cotton, 499 
Sorting, 453 

South African goatskins, 27 
South American hides, 18 
Southern Europe goatskins, 25 



698 



INDEX 



Spanish goatskins, 23 

leather, 340 
Specific gravity of liquids, 674 

tables, 673 
Speed of pulleys, 679 
Sphere, volume of, 679 
Spirit black, 343 
Splits for white shoes, 153 

heavy, 328 

vegetable-tanned, 325 

white, 152 
Splitting, 132 

after tanning, 133 

out of. aluminum sulphate and 
salt pickle 132, 
lime, 131 
pickle, 132, 133 
Splitter, Union, 246 
Splits, finishing for, 486 

grain leather from, 491 
Sporting goods leathers, 478 
Spray dyeing, 379 
Spready cows, 17 

hides, 16 
Spring style fleshing knife, 81 
Sprinkler leach, 532 
Square measure, 675 
Stag horn, 553 
Stains, removal of, 483 
Staker, knee, 150 
Staking, 450, 457 

machine, 456 
Staling, 72 
Steam, 679 

temperature of, 682 
Steers, Colorado, 17 

uative, 16 

Texas, 17 
Stiasny, cited, 558 
Sticker, 3 
Stick-lac, 498 
Stocks, 59 

fulling, 59 
Stoning-jack, 249 
Straight hides, 18 
Strap leather, 318 

chrome, 183 
Stretching, 315 
Stripping, 451 

the tannage, 204 
Structure of hides, 48 
Stuck-throats, 3 

Stuffing chrome lace leather, 445 
Sturtevant dryer, 451, 452 
Substantive dyes, 352 
Sudan goatskins, 27 
Suede leather, 237 

coloring, 392 

marbled, 413 



Sulphide-lime liquors, analysis of, 
597 
process for sides, 95 
Sulphite cellulose extract, 556 
Sulphonated hydrocarbons, 566 
oils, 434, 437 
analysis of, 640 
on chrome leather, 440 
sole leather, 441 
vegetable-tanned leather, 440 
Sulphuric acid and salt pickle, 
127 
in de-liming, 111 
in leather, 646 
Sumac, 368, 552 
mordant, 365, 397 
simple test for, 663 
tannage, 228 
Suppleness to increase, 192 
Surveyor's measure, 675 
Sweat glands, 49 
Sweat pit, 71 
Sweating, 71 
Sweep tare, 13 
Swiss hides, 19 
Syntans, 558 
Synthetic tanning materials, 558 

Tacking, 451 
Tail-puller, 9 
Taking-up hides, 12 
Tan liquors, 612 

shades, 398 

yard, 274, 276 
Tannage, alum, 138 

formaldehyde, 147 

shark-liver oil, 135 
Tannery waste, 665 

disposal of, 665 
Tanning agents for belting 
leather, 295 

buckskins, 154 

extracts, sampling of, 620 

glossary of terms used in, 683- 
687 

in paddle-vat, 169 

materials, quantities for analy- 
sis, 611 

pigskins, 255 
- snakeskins, 247 

with formaldehyde, 156 
Tanolin, 165 
Tanolin T, 189 
Tartar emetic, 399 
Tea's extractor, 613 
Tensile strength, 292 
Terms used in tanning, glossary 

of, 683-687 
Test for de-liming, 111 
Texas steers, 17 



INDEX 



699 



Theory of chrome tanning, 198 
Thermometers, comparison of, 
671 

conversions, 670 
Ticks, sheep, 33 
Titanium-potassium oxalate, 365 

analysis of, 654 
Titer test, 654 
Toggled, 79 
Tray dyeing, 356 
Troy weight, 674 
Tryptase, 86 
Turkestans, 26 
Turkish goatskins, 25 
Turner embossing press, 339 

serial table machine, 313 
Turpentine, 342 
Twisters, 161 

Two-bath chrome liquors, analy- 
sis of, 603 

on pickled sheepskins, 163 

process, 158 
of chrome tannage, new, 171 

Ultra-violet light, 347 
Umber, 343 
Unhairing, 86 

machine, 80, 93 
Union leather, 272 

splitter, 246 
United States Government regu- 
lations for hides, etc., 37-45 
Units of heat, 680 
Unsplit sides, 177 
Unusual tanning processes, 567 
Useful data, 670 

Vacuum evaporation, 537 

tanning, 568 
Valonia, 551 
Varnish, 345 

collodion, 380 
Vaughn machine, 308 
Vegechrome, 204 
Vegetable tanning materials, 525, 
611 
grinding, 526 
Vegetable-tanned calfskins, black, 
390 
• fat-liquor for, 432 
grain, finish for, 478 
kangaroo, 240 
leather, analysis of, 625 
blacking for, 485 
dyeing, 356 
sulphonated oil on, 440 



light leather, 225 

sheepskins, 225 

side leather, 242 
fat-liquor for, 428 

skins, dyeing, 374 

upper leather, dyeing of, 411 
Velvet leather, 237 

chrome, 187 

coloring, 392 
Vici kid, 433 
Viscosity, 651 

Wallaby, 67 

Walrus grain seal, 252 
Warble, 2 

fly, 14 
Warm sweat, 71, 72 
Washing hides, 57 

pigskins, 68 
Wash-wheel, 56 
Water analysis, 585 

solubles in leather, 638 
Waterproof dressing:, 485 

filling for sole leather, 443 
Wattle bark, 556 
Wax calf, chrome-tanned, 207 

resist, 380 
Waxed splits, 329 
Waxes, 419 
Weight of liquids, 674 

pipes, 670 
Welting, 318 
Wetting-back, 30? 
Wheel stuffing, 311 
White buckskins, 155 

calfskin leather, 145 

chrome, 189 

chrome-tanned sheepskins, 168 

furs, cleaning of, 515 

pigskins, 151 

side leather, 185 

splits, 152 
Whitening, 320 

machine, 309 
Wool, disinfection of, 40 
Woolskins, 501 

chrome-tanned, 513 

coloring, 506 

de-greasing, 504 

dyeing, 517 

formaldehyde tannage, 504 

tanning, 501 
Wyncoop, G., cited, 578 

Zinc chloride, 52 

sulphate in de-liming, 116 



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